Adding `ssize_t_cast` to support passing `size_t` or `ssize_t` values where `ssize_t` is needed. (#3219)
* Trivial change to avoid (ssize_t) cast.
* Demo for safe_ssize_t idea.
* Removing safe_ssize_t.cpp (proof-of-concept code) to not upset the GHA Format workflow.
* Completing changes in pytypes.h
* New ssize_t_cast (better replacement for safe_ssize_t).
* clang-format-diff (no manual changes).
* bytes_ssize_t -Wnarrowing reproducer (see PR #2692).
* Backing out tuple(), list() ssize_t support, for compatibility with older compilers (to resolve link failures).
* Bug fix: missing `py::` for `py::ssize_t`
* Restoring tuple(), list() ssize_t support, but passing `size` by value, for compatibility with older compilers (to resolve link failures).
* Full test coverage of all functions with modified signatures.
