Re-evaluate if typing_extensions is still needed as a vendored dependency for pkg_resources

[abravalheri]

This (typing_extensions) was not listed. The vendored.txt file says the following:

# required for platformdirs on Python < 3.8
typing_extensions==4.4.0

But now we removed support to Python < 3.8, so I guess we can remove this vendored dependency?

Originally posted by @abravalheri in #4320 (comment)

[Avasam]

I'd be surprised if we can't just hide whatever usage of typing_extensions behind TYPE_CHECKING checks and from __future__ import annotations.

[Avasam]

On setuptools' side, jaraco.text is causing a chain of dependencies: inflect --> typeguard --> typing_extensions. These can all be removed with jaraco/jaraco.text#16