* Fix MSVC MT/MD incompatibility in PYBIND11_BUILD_ABI

* Update comment about which PR

* Use msvc major version

* Use _MSC_VER/100

* Fix figuring out MD vs MT

* Add some test runs

* Skip one test

* Fix preprocessor

* simplify code

* fix if

* support only msvc 19

* Fold in changes from experimental PR #5411. Polish error messages.

* Remove `&& defined(_DLL)` (TBD: is it needed? but what is correct?)

* Fix MT vs MD

* Add a couple comments, based on https://github.com/pybind/pybind11/pull/4953#issuecomment-2435138593 (posted by @isuruf).

* Replace misleading comment: NVHPC is NOT outdated.

* Update include/pybind11/detail/internals.h

Co-authored-by: Robert Maynard <robertjmaynard@gmail.com>

---------

Co-authored-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgkio@gmail.com>
Co-authored-by: Robert Maynard <robertjmaynard@gmail.com>