Setuptools should not rely on pkg_resources

[jaraco]

This issue basically tracks the root goal of obviating pkg_resources, in particular that Setuptools depends on it.

Over the past few years, myself and others have worked hard to create importlib.resources and importlib.metadata in the goal of superseding pkg_resources. These libraries are now very stable and replacing much of the functionality provided by pkg_resources.

In python/importlib_metadata#38, I examined the setuptools package to determine its level of dependency on pkg_resources. Unsurprisingly, there is a diverse set of interfaces on which setuptools relies.

Nevertheless, this project should work toward Setuptools adopting the importlib features in place of pkg_resources.

[romuald]

This somehow breaks projects entry points to pyramid/paste it seems, which aren't able to find their entry point anymore (I have no idea what's the cause)

Error for Google:

LookupError: Entry point 'main' not found in egg 'my.package' (dir: xxx/.pyenv-python3.7/lib/python3.7/site-packages; protocols: paste.app_factory, paste.composite_factory, paste.composit_factory; entry_points: )

[armanckeser]

The same pr causes this issue I think #3102