Remove unnecessary code paths for 3.9+ (follow up on skeleton changes)

[abravalheri]

Follow-up on e47994c.

Summary of changes

• Bump version check in pkg_resources
• Remove 'm' SOABI flag that no longer exists in 3.9+
  • See https://docs.python.org/3/library/sys.html#sys.abiflags
• Remove conditional requirement on importlib_resources in favour of importlib.resources
• Removed vendored version of importlib_resources
  • Probably this is the most risky changes, but it seems that no vendored dependencies require it for 3.9+
  • If 3rdparty packages are relying on the vendored version in setuptools, I think it is fair that they start to fail... It is not a good development practice to rely on indirect dependencies - instead they should be declared directly.

Closes

Pull Request Checklist

• Changes have tests
• News fragment added in newsfragments/.
  (See documentation for details)

[abravalheri]

I have added the news fragments as feature, although they are removals...
For 3.9+, this should not matter much.

This approach seems to be consistent with the existing changelog that classifies these changes in requires-python as features.

I can rename the news fragment files if necessary.

[Avasam]

• You can move setuptools._path.StrPath out of the TYPE_CHECKING check !
• functools.lru_cache(maxsize=None) can be replaced by functools.cache *
• Callable, Generator, Iterator, Iterable, Sequence, Mapping, MutableMapping should be imported from collections.abc instead of typing *
• Type, Dict, List, Tuple should be replaced by their builtin variant *
• Optional should be replaced by Union for consistency

*UP035 (which includes https://github.com/PyCQA/flake8-pyi/blob/main/ERRORCODES.md#Y022 ) should catches those, but it looks like the include = ["pyproject.toml"] workaround broke it ! :O

I think include = ["pyproject.toml"] should be replaced by target-version = "py39" # Target the oldest supported Python version . The comment and link are still correct.

Edit: because it should be extend = "pyproject.toml", not include...

[Avasam]

Additional tidbit I found: setuptools.package_index._splituser has a comment about Python 3.8, but it would be nice if it linked to python/cpython#80072

[abravalheri]

Thank you @Avasam, I implemented the suggestions in:

• Automatic updates from Ruff for Python 3.9+ #4721
• Move setuptools._path.StrPath out of the if TYPE_CHECKING (Python 3.9+) #4722
• Add comment explaining the origin of workaround for _splituser #4723

I am leaving the fix to ruff.toml to skeleton, we can see the feedback there and then decide what to do.