* First pass updating misc files, informed by https://github.com/pybind/pybind11/pull/5177/commits

* Remove jobs using silkeh/clang and gcc docker containers that come with Python 3.7

* Add silkeh/clang:17-bookworm

* Add job using GCC 7

* Revert "Add job using GCC 7"

This reverts commit 518515a761ac37dc2cf5d0980da82d0de39edc28.

* Try running in ubuntu-18.04 container under ubuntu-latest (to get GCC 7)

* Fix `-` vs `:` mixup.

* This reverts commit b1c4304475b8ad129c12330c7ed7eb85d15ba14a.

Revert "Try running in ubuntu:18.04 container under ubuntu-latest (to get GCC 7)"

This reverts commit b203a294bb444fc6ae57a0100fa91dc91b8d3264.

* `git grep 0x03080000` cleanup.

* `git grep -I -E '3\.7'` cleanup.

Removes two changes made under pybind/pybind11#3702

* Revert "`git grep -I -E '3\.7'` cleanup."

This reverts commit bb5b9d187bffbfb61e2977d7eee46b766fa1cce9.

* Remove comments that are evidently incorrect:

```
...
-- The CXX compiler identification is Clang 15.0.7
...
- Found Python: /usr/bin/python3.9 (found suitable version "3.9.2", minimum required is "3.7") found components: Interpreter Development.Module Development.Embed
...
/__w/pybind11/pybind11/include/pybind11/gil.h:150:13: error: 'auto key' can be declared as 'auto *key' [readability-qualified-auto,-warnings-as-errors]
            auto key = internals.tstate;
            ^~~~~
            auto *
/__w/pybind11/pybind11/include/pybind11/gil.h:174:13: error: 'auto key' can be declared as 'auto *key' [readability-qualified-auto,-warnings-as-errors]
            auto key = detail::get_internals().tstate;
            ^~~~~
            auto *
```

* .github/workflows/configure.yml: Change from Python 3.7 to 3.8

* Misc cleanup pass

* Miscellaneous changes based on manual review of the `git grep` matches below:

```
git_grep_37_38.sh |& sort | uniq -c
```

With git_grep_37_38.sh:

```
set -x
git grep 0x0307
git grep 0x0308
git grep PY_MINOR_VERSION
git grep PYPY_VERSION
git grep -I -E '3\.7'
git grep -I -E '3\.8'
git grep -I -E '\(3, 7'
git grep -I -E '\(3, 8'
git grep -I -E '3[^A-Za-z0-9.]+7'
git grep -I -E '3[^A-Za-z0-9.]+8'
```

Output:

```
      1 .appveyor.yml:    $env:CMAKE_INCLUDE_PATH = "eigen-3.3.7;$env:CMAKE_INCLUDE_PATH"
      1 .appveyor.yml:    7z x eigen-3.3.7.zip -y > $null
      1 .appveyor.yml:    Start-FileDownload 'https://gitlab.com/libeigen/eigen/-/archive/3.3.7/eigen-3.3.7.zip'
      1 CMakeLists.txt:    # Bug in macOS CMake < 3.7 is unable to download catch
      1 CMakeLists.txt:  elseif(WINDOWS AND CMAKE_VERSION VERSION_LESS 3.8)
      1 CMakeLists.txt:  if(OSX AND CMAKE_VERSION VERSION_LESS 3.7)
      1 CMakeLists.txt:    message(WARNING "CMAKE 3.7+ needed on macOS to download catch, and newer HIGHLY recommended")
      1 CMakeLists.txt:    message(WARNING "CMAKE 3.8+ tested on Windows, previous versions untested")
      1 CMakeLists.txt:    # Only tested with 3.8+ in CI.
      1 docs/advanced/functions.rst:Python 3.8 introduced a new positional-only argument syntax, using ``/`` in the
      1 docs/changelog.rst:* Adapt pybind11 to a C API convention change in Python 3.8. `#1950
      1 docs/changelog.rst:* Allow thread termination to be avoided during shutdown for CPython 3.7+ via
      1 docs/changelog.rst:  considered as conversion, consistent with Python 3.8+.
      1 docs/changelog.rst:  CPython 3.8 and 3.9 debug builds.
      1 docs/changelog.rst:* Enum now has an ``__index__`` method on Python <3.8 too.
      1 docs/changelog.rst:  on Python 3.8. `#1780 <https://github.com/pybind/pybind11/pull/1780>`_.
      1 docs/changelog.rst:* PyPy 3.10 support was added, PyPy 3.7 support was dropped.
      2 docs/changelog.rst:* Support PyPy 7.3.7 and the PyPy3.8 beta. Test python-3.11 on PRs with the
      1 docs/changelog.rst:* Use ``macos-13`` (Intel) for CI jobs for now (will drop Python 3.7 soon).
      1 docs/changelog.rst:* Use new Python 3.7 Thread Specific Storage (TSS) implementation if available.
      1 docs/compiling.rst:    cmake -DPYBIND11_PYTHON_VERSION=3.8 ..
      1 docs/compiling.rst:    find_package(Python 3.8 COMPONENTS Interpreter Development REQUIRED)
      1 docs/limitations.rst:- PyPy3 7.3.1 and 7.3.2 have issues with several tests on 32-bit Windows.
      1 docs/requirements.txt:idna==3.7 \
      1 + git grep 0x0307
      1 + git grep 0x0308
      1 + git grep -I -E '\(3, 7'
      1 + git grep -I -E '3\.7'
      1 + git grep -I -E '\(3, 8'
      1 + git grep -I -E '3\.8'
      1 + git grep -I -E '3[^A-Za-z0-9.]+7'
      1 + git grep -I -E '3[^A-Za-z0-9.]+8'
      1 + git grep PY_MINOR_VERSION
      1 + git grep PYPY_VERSION
      2 .github/workflows/ci.yml:        - '3.8'
      1 .github/workflows/ci.yml:        - 3.8
      1 .github/workflows/ci.yml:    - name: Add Python 3.8
      1 .github/workflows/ci.yml:        - 'pypy-3.8'
      2 .github/workflows/ci.yml:            python: '3.8'
      1 .github/workflows/ci.yml:          - python: '3.8'
      1 .github/workflows/ci.yml:          - python: 3.8
      1 .github/workflows/ci.yml:            python: 'pypy-3.8'
      1 .github/workflows/configure.yml:          cmake: "3.8"
      1 .github/workflows/configure.yml:    name: 🐍 3.8 • CMake ${{ matrix.cmake }} • ${{ matrix.runs-on }}
      1 .github/workflows/configure.yml:    - name: Setup Python 3.8
      1 .github/workflows/configure.yml:        python-version: 3.8
      1 .github/workflows/pip.yml:    name: 🐍 3.8 • 📦 & 📦 tests • ubuntu-latest
      1 .github/workflows/pip.yml:    name: 🐍 3.8 • 📦 tests • windows-latest
      2 .github/workflows/pip.yml:    - name: Setup 🐍 3.8
      2 .github/workflows/pip.yml:        python-version: 3.8
      2 include/pybind11/cast.h:#if !defined(PYPY_VERSION)
      2 include/pybind11/cast.h:#if defined(PYPY_VERSION)
      2 include/pybind11/cast.h:            // PyPy: 7.3.7's 3.8 does not implement PyLong_*'s __index__ calls.
      5 include/pybind11/detail/class.h:#if !defined(PYPY_VERSION)
      1 include/pybind11/detail/class.h:#if defined(PYPY_VERSION)
      1 include/pybind11/detail/class.h:    // This was not needed before Python 3.8 (Python issue 35810)
      1 include/pybind11/detail/common.h:    && !defined(PYPY_VERSION) && !defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
      2 include/pybind11/detail/common.h:#    error "PYTHON < 3.8 IS UNSUPPORTED. pybind11 v2.13 was the last to support Python 3.7."
      1 include/pybind11/detail/common.h:#if defined(PYPY_VERSION) && !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
      1 include/pybind11/detail/common.h:#if PY_VERSION_HEX < 0x03080000
      1 include/pybind11/detail/common.h:            = PYBIND11_TOSTRING(PY_MAJOR_VERSION) "." PYBIND11_TOSTRING(PY_MINOR_VERSION);        \
      1 include/pybind11/detail/internals.h:        // called. PYBIND11_TLS_FREE is PyThread_tss_free on python 3.7+. On older python, it does
      1 include/pybind11/detail/internals.h:#if PYBIND11_INTERNALS_VERSION <= 4 || defined(PYPY_VERSION)
      1 include/pybind11/detail/internals.h:// The old Python Thread Local Storage (TLS) API is deprecated in Python 3.7 in favor of the new
      1 include/pybind11/detail/type_caster_base.h:#if defined(PYPY_VERSION)
      1 include/pybind11/embed.h:#    define PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX (0x03080000)
      1 include/pybind11/embed.h:#if defined(PYPY_VERSION)
      1 include/pybind11/eval.h:    // globals if not yet present.  Python 3.8 made PyRun_String behave
      2 include/pybind11/eval.h:#if defined(PYPY_VERSION)
      2 include/pybind11/eval.h:    // was missing from PyPy3.8 7.3.7.
      2 include/pybind11/gil.h:    /// allowed during shutdown. Check _Py_IsFinalizing() on Python 3.7+, and
      1 include/pybind11/pybind11.h:#if !defined(PYPY_VERSION)
      4 include/pybind11/pybind11.h:#if !defined(PYPY_VERSION) && PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 9
      1 include/pybind11/pytypes.h:#endif //! defined(PYPY_VERSION)
      2 include/pybind11/pytypes.h:#if !defined(PYPY_VERSION)
      1 include/pybind11/pytypes.h:#    if defined(PYPY_VERSION_NUM) && PYPY_VERSION_NUM < 0x07030a00
      1 include/pybind11/pytypes.h:#ifdef PYPY_VERSION
      1 include/pybind11/stl/filesystem.h:#    if !defined(PYPY_VERSION)
      2 pybind11/__init__.py:if sys.version_info < (3, 8):
      2 pybind11/__init__.py:    msg = "pybind11 does not support Python < 3.8. v2.13 was the last release supporting Python 3.7."
      1 pyproject.toml:master.py-version = "3.8"
      1 pyproject.toml:python_version = "3.8"
      1 README.rst:lines of code and depend on Python (3.8+, or PyPy) and the C++
      2 README.rst:- Python 3.8+, and PyPy3 7.3 are supported with an implementation-agnostic
      1 setup.cfg:    Programming Language :: Python :: 3.8
      1 setup.cfg:python_requires = >=3.8
      1 setup.py:# TODO: use literals & overload (typing extensions or Python 3.8)
      1 tests/CMakeLists.txt:if(NOT CMAKE_VERSION VERSION_LESS 3.8)
      2 tests/constructor_stats.h:#if defined(PYPY_VERSION)
      1 tests/env.py:    doesn't work on CPython 3.8.0 with pytest==3.3.2 on Ubuntu 18.04 (#2922).
      1 tests/requirements.txt:build~=1.0; python_version>="3.8"
      1 tests/requirements.txt:numpy~=1.21.5; platform_python_implementation!="PyPy" and python_version>="3.8" and python_version<"3.10"
      1 tests/requirements.txt:numpy~=1.23.0; python_version=="3.8" and platform_python_implementation=="PyPy"
      1 tests/test_buffers.py:    env.PYPY, reason="PyPy 7.3.7 doesn't clear this anymore", strict=False
      1 tests/test_builtin_casters.py:    # Before Python 3.8, `PyLong_AsLong` does not pick up on `obj.__index__`,
      2 tests/test_builtin_casters.py:    if (3, 8) <= sys.version_info < (3, 10) and env.CPYTHON:
      4 tests/test_builtin_casters.py:    # TODO: PyPy 3.8 does not behave like CPython 3.8 here yet (7.3.7)
      1 tests/test_callbacks.py:    assert m.test_callback3(z.double) == "func(43) = 86"
      2 tests/test_call_policies.cpp:#if !defined(PYPY_VERSION)
      1 tests/test_chrono.py:    diff = m.test_chrono_float_diff(43.789012, 1.123456)
      1 tests/test_constants_and_functions.py:    assert m.f3(86) == 89
      1 tests/test_eigen_matrix.py:    a_copy3[8, 1] = 11
      1 tests/test_eigen_matrix.py:    assert np.all(cornersc == np.array([[1.0, 3], [7, 9]]))
      1 tests/test_eigen_matrix.py:    assert np.all(cornersr == np.array([[1.0, 3], [7, 9]]))
      1 tests/test_eigen_matrix.py:        mymat = chol(np.array([[1.0, 2, 4], [2, 13, 23], [4, 23, 77]]))
      1 tests/test_exceptions.py:    if hasattr(pytest, unraisable):  # Python >= 3.8 and pytest >= 6
      2 tests/test_exceptions.py:@pytest.mark.xfail(env.PYPY, reason="Failure on PyPy 3.8 (7.3.7)", strict=False)
      1 tests/test_factory_constructors.py:    assert [i.alive() for i in cstats] == [13, 7]
      1 tests/test_kwargs_and_defaults.cpp:#ifdef PYPY_VERSION
      1 tests/test_local_bindings.py:    assert i1.get3() == 8
      1 tests/test_methods_and_attributes.cpp:#if !defined(PYPY_VERSION)
      1 tests/test_numpy_array.py:    a = np.arange(3 * 7 * 2) + 1
      1 tests/test_numpy_array.py:    assert str(excinfo.value) == "cannot reshape array of size 42 into shape (3,7,1)"
      2 tests/test_numpy_array.py:    assert x.shape == (3, 7, 2)
      2 tests/test_numpy_array.py:        m.reshape_tuple(a, (3, 7, 1))
      2 tests/test_numpy_array.py:    x = m.reshape_tuple(a, (3, 7, 2))
      1 tests/test_numpy_vectorize.py:    assert np.isclose(m.vectorized_func3(np.array(3 + 7j)), [6 + 14j])
      1 tests/test_pickling.cpp:#if !defined(PYPY_VERSION)
      1 tests/test_pytypes.cpp:#if (defined(__APPLE__) && defined(__clang__)) || defined(PYPY_VERSION)
      1 tests/test_smart_ptr.cpp:    m.def("make_myobject3_1", []() { return new MyObject3(8); });
      1 tests/test_smart_ptr.py:    assert cstats.values() == ["MyObject3[9]", "MyObject3[8]", "MyObject3[9]"]
      1 tests/test_stl_binders.py:    assert v_int2 == m.VectorInt([0, 99, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 88])
      1 tests/test_stl_binders.py:    assert v_int2 == m.VectorInt([0, 99, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 88, 4])
      1 tests/test_type_caster_pyobject_ptr.cpp:#if !defined(PYPY_VERSION) // It is not worth the trouble doing something special for PyPy.
      1 tools/FindPythonLibsNew.cmake:  set(PythonLibsNew_FIND_VERSION "3.8")
      1 tools/JoinPaths.cmake:# https://docs.python.org/3.7/library/os.path.html#os.path.join
      1 tools/pybind11NewTools.cmake:    Python 3.8 REQUIRED COMPONENTS ${_pybind11_interp_component} ${_pybind11_dev_component}
      1 tools/pybind11NewTools.cmake:# Python debug libraries expose slightly different objects before 3.8
      1 tools/pybind11Tools.cmake:    "3.12;3.11;3.10;3.9;3.8"
      1 tools/pybind11Tools.cmake:    if(NOT DEFINED PYPY_VERSION)
      1 tools/pybind11Tools.cmake:    message(STATUS "PYPY ${PYPY_VERSION} (Py ${PYTHON_VERSION})")
      1 tools/pybind11Tools.cmake:# Python debug libraries expose slightly different objects before 3.8
      1 tools/pybind11Tools.cmake:      set(PYPY_VERSION
```

* Change `[tool.ruff]` `target-version` to `"py38"`, as suggested by @Skylion007