gh-111178: fix UBSan failures in Modules/xx*.c

[picnixz]

This PR fixes the UBSan failures and addresses some minor cosmetic changes. PEP-7 changes were not applied since they could scramble the diff but other semantic changes affecting the signature of touched functions may have been done.

• Issue: UBSan: Calling a function through pointer to incorrect function type is undefined behavior #111178

[picnixz]

Ah I'm sorry I put this one as ready for review but I learned that _ + capital letter was also UB (#128248 (comment)) so I'll fix them tomorrow.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Debian root 3.x has failed when building commit ead0913.

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/345/builds/10373) and take a look at the build logs.
4. Check if the failure is related to this commit (ead0913) 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/345/builds/10373

Failed tests:

• test_os

Failed subtests:

• test_timerfd_ns_poll - test.test_os.TimerfdTests.test_timerfd_ns_poll

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

==

Click to see traceback logs

Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/test_os.py", line 4506, in test_timerfd_ns_poll
    self.check_timerfd_poll(True)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/test_os.py", line 4491, in check_timerfd_poll
    self.assertEqual(self.read_count_signaled(fd), 1)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 3 != 1


Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/test_os.py", line 4506, in test_timerfd_ns_poll
    self.check_timerfd_poll(True)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/test_os.py", line 4491, in check_timerfd_poll
    self.assertEqual(self.read_count_signaled(fd), 1)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 2 != 1