gh-103092: Test _ctypes type hierarchy and features

[aisk]

This change is related to #113620 (review), to test the compatibility before and after it.

All classes with metatypes (which have changed in #113620) are tested, plus CField. Other classes are hard to test (can't be accessed in Python easily), or Windows related (I'm not using Windows now), I think it's better to add tests to test them in another PR.

@erlend-aasland

• Issue: Isolate Stdlib Extension Modules #103092

[aisk]

Thanks for the review. All issues mentioned in the comments above should now be fixed.

And I renamed support.py to _support.py, otherwise it will cause an ambiguous import when running with -R : argument:

Traceback (most recent call last):
File "C:\Users\xxxxx\Source\cpython\Lib\unittest\loader.py", line 113, in loadTestsFromModule
return load_tests(self, tests, pattern)
~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\xxxxx\Source\cpython\Lib\test\test_ctypes\__init__.py", line 10, in load_tests
return support.load_package_tests(os.path.dirname(__file__), *args)
^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'test.test_ctypes.support' has no attribute 'load_package_tests'

[aisk]

Lots of CIs have failed, seems to be related to GitHub's internal error, and this page often returns 500. I think we should re-run the CI after GitHub fixes the server error.