gh-92906: Enable test_cppext on Windows

[jkloth]

With source build virtual environments sorted out, this test also runs just fine on Windows. Requires #92897.

Adding @vstinner due to recent work on this test.

[jkloth]

The Windows test failures are to be expected until #92897 is resolved.

[serhiy-storchaka]

There are merge conflicts now. It may be easier to recreate this change from scratch than try to resolve them.

[vstinner]

I tried to add the following code to setup.py, but setup.py stil fails to find python313_d.lib, it looks for python313.lib :-(

    include_dirs = []
    library_dirs = []
    if support.MS_WINDOWS:
        # pyconfig.h is created in PCbuild\amd64\
        # python313.lib is created in  PCbuild\amd64\
        src_dir = dirname(dirname(dirname(os.getcwd())))
        build_dir = os.path.join(src_dir, 'PCbuild', 'amd64')
        include_dirs.append(build_dir)
        library_dirs.append(build_dir)

[vstinner]

I wrote a new PR from scratch: #117000

PR are now run on Windows, but only on release build.