gh-101476: Use _PyType_GetModuleState where applicable

[erlend-aasland]

• Issue: Add internal API for fast module access from heap type methods #101476

[erlend-aasland]

I consider this a trivial and non-controversial PR; I intend to merge it as soon as the CI is green. If this turns out to be bad judgement from my side, I'm happy to revert it.

[corona10]

If this turns out to be bad judgement from my side, I'm happy to revert it.

I remember that there were some kinds of discussions to use public API as possible.
I will let you know once I find it.

cc @ericsnowcurrently

[corona10]

Might be one piece of discussion I remember: #90699 (comment)

[ericsnowcurrently]

At least with _xxsubinterpreters, I purposefully did not use any internal API. Ideally, non-builtin extensions would avoid internal API, generally.

[erlend-aasland]

@ericsnowcurrently, @corona10: As the PR title says, I've only applied this where applicable. This implies extension modules that define Py_BUILD_CORE_BUILTIN 1. For extension modules without this define, no change has been made.

[erlend-aasland]

I've reverted the change in _testmultiphase.

[ericsnowcurrently]

BTW, thanks for working on this, @erlend-aasland!

[erlend-aasland]

Thanks for comments and reviews, everyone!