`pkg_resources`: Expose the type of imports and re-exports

[Avasam]

Summary of changes

• ~~Removed unused resource_dir and resource_dir~~ #4260
• ~~Removed overriden run_main and run_script~~ #4260
• ~~Moved declarations of @_call_aside defined globals closer to where they're defined. And after ResourceManager & WorkingSet to avoid forward reference issues~~ #4267
• ~~Typed the 3 globals set by _declare_state as not None~~ #4258
• Statically exposed the dynamic imports using a TYPE_CHECKING block and static imports

Works towards #2345 and a big step towards merging typeshed's pkg_resources stubs into setuptools

Pull Request Checklist

• [ ] Changes have tests (this is to help with type-checking checks)
• [ ] News fragment added in newsfragments/. (See documentation for details)

[Avasam]

Setting as draft to make it clear this isn't a priority to review. Will probably end up being the last pkg_resources PR for static typing.

[Avasam]

Superseded by #4457 , thanks @jaraco !

Static typing issues caused by vendored packages can now also be fixed upstream