pkgconf-pypi

I cleaned up the changes I had started working on last month, and opened pypackaging-native/pkgconf-pypi#105.

As discussed previously, it moves the Python integration functionality to a new pkgconf-pypi executable. pkgconf and pkg-config now provide regular pkgconf executables, just without the capacity to search the system, requiring the user to define PKG_CONFIG_PATH.

CPython

My PR freezing the encodings module (python/cpython#145279) was reverted due to a failure on Windows.

From a quick look, it might seem like it was just missing freezing the encodings._win_cp_codecs submodule, but I doubt that's all. Unless the standard library is missing, the import machinery should have been able to import the submodule from the file-system.

I need to look into it with more detail, and likely add a couple tests.

The 3.15 feature lock is only two months away, and I really want to get this change in, so I need hurry a little bit.