gh-141004: Document Py_LOCAL*

[StanFromIreland]

• Issue: Document the entire C API #141004

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📚 Documentation preview 📚: https://cpython-previews--141725.org.readthedocs.build/

[willingc]

☀️ Thanks Stan.

[StanFromIreland]

Thanks for the review!

[miss-islington-app]

Thanks @StanFromIreland for the PR, and @ZeroIntensity for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-141761 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-141762 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 MacOS M1 Refleaks NoGIL 3.13 (tier-2) has failed when building commit 49ac2bb.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1396/builds/1794) and take a look at the build logs.
4. Check if the failure is related to this commit (49ac2bb) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1396/builds/1794

Failed tests:

• test.test_multiprocessing_spawn.test_processes
• test.test_multiprocessing_forkserver.test_processes
• test.test_concurrent_futures.test_shutdown

Failed subtests:

• test_repr_rlock - test.test_multiprocessing_forkserver.test_processes.WithProcessesTestLock.test_repr_rlock
• test_repr_rlock - test.test_multiprocessing_spawn.test_processes.WithProcessesTestLock.test_repr_rlock

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.13.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/test/_test_multiprocessing.py", line 1492, in test_repr_rlock
    self.assertEqual('<RLock(SomeOtherThread, nonzero)>', repr(lock))
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: '<RLock(SomeOtherThread, nonzero)>' != '<RLock(None, 0)>'
- <RLock(SomeOtherThread, nonzero)>
+ <RLock(None, 0)>


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.13.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/test/_test_multiprocessing.py", line 1492, in test_repr_rlock
    self.assertEqual('<RLock(SomeOtherThread, nonzero)>', repr(lock))
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: '<RLock(SomeOtherThread, nonzero)>' != '<RLock(SomeOtherProcess, nonzero)>'
- <RLock(SomeOtherThread, nonzero)>
?                 ^^  ^^
+ <RLock(SomeOtherProcess, nonzero)>
?                 ^ ++ ^^


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.13.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/threading.py", line 1044, in _bootstrap_inner
    self.run()
    ~~~~~~~~^^
  File "/Users/buildbot/buildarea/3.13.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/concurrent/futures/process.py", line 363, in run
    executor._adjust_process_count()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/buildbot/buildarea/3.13.itamaro-macos-arm64-aws.macos-with-brew.refleak.nogil/build/Lib/concurrent/futures/process.py", line 759, in _adjust_process_count
    process_count = len(self._processes)
TypeError: object of type 'NoneType' has no len()