Forbid imports of collections.abc aliases from typing

[AlexWaygood]

A regression test for python/typeshed#7635

Refs #46 (but doesn't quite close it).

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Changes made

• Expand Y027 to cover all objects in typing that are aliases to objects in collections.abc, except for AbstractSet
• Add new Y038 error code to forbid import AbstractSet from typing
• Change the error message in Y023 to make it clear that imports from collections.abc are now preferred to imports from typing.
• Refactor Y023 logic in pyi.py so as to quell flake8 from complaining that _check_import_or_attribute was getting too complex.
• Some small refactorings of test files to make them compatible with the new checks.

[AlexWaygood]

• Use PEP 585 syntax in collections python/typeshed#7657 for the collections hits
• The output of typeshed_primer makes it look like there's a lot of hits in _collections_abc and builtins, but in reality, we only need one # noqa comment in each module, since all the imports are on the same line. Combined with the hit in types and the hit in array, we'll need to add 4 # noqa comments to typeshed if we merge this.

[AlexWaygood]

typeshed PR to add the required # noqas:

• Add a few # noqas python/typeshed#7658