GH-128520: Merge pathlib._abc into pathlib.types

[barneygale]

There used to be a meaningful distinction between these modules: pathlib imported pathlib._abc but not pathlib.types, and so zero-cost type annotations could only be added to the latter. This is no longer the case (neither module is imported), so we move the ABCs as follows:

• pathlib._abc.JoinablePath --> pathlib.types._JoinablePath
• pathlib._abc.ReadablePath --> pathlib.types._ReadablePath
• pathlib._abc.WritablePath --> pathlib.types._WritablePath

The pathlib._abc module is deleted.

• Issue: Make pathlib ABCs usable by zipfile.Path #128520

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Ubuntu Shared 3.x (tier-1) has failed when building commit d0eb01c.

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/506/builds/10011) and take a look at the build logs.
4. Check if the failure is related to this commit (d0eb01c) 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/506/builds/10011

Failed tests:

• test.test_concurrent_futures.test_process_pool

Failed subtests:

• test_force_shutdown_workers - test.test_concurrent_futures.test_process_pool.ProcessPoolSpawnProcessPoolExecutorTest.test_force_shutdown_workers
• test_force_shutdown_workers - test.test_concurrent_futures.test_process_pool.ProcessPoolForkProcessPoolExecutorTest.test_force_shutdown_workers

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/test_importlib/metadata/fixtures.py", line 391, in _inner
    func(self, **args)
    ~~~~^^^^^^^^^^^^^^
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/test_concurrent_futures/test_process_pool.py", line 279, in test_force_shutdown_workers
    self.assertEqual(worker_process.exitcode, -signal.SIGTERM)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 255 != -15


Traceback (most recent call last):
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/test_importlib/metadata/fixtures.py", line 391, in _inner
    func(self, **args)
    ~~~~^^^^^^^^^^^^^^
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/test/test_concurrent_futures/test_process_pool.py", line 281, in test_force_shutdown_workers
    self.assertEqual(worker_process.exitcode, -signal.SIGKILL)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 255 != -9