managers, meta: migrate off of pkg_resources to importlib_metadata

[dgw]

This fixes installing sopel (which depends on this package) from scratch on a new environment that does not ship with pkg_resources as part of the Python stdlib (py3.12+) and also omits setuptools (some distros, fresh venvs, probably others).

Also includes slight cleanup of comments, log messages, and imports, but I think not enough to be worth a separate commit or pull request.

Progresses #11, but not all the way to completion (it asks for importlib.metadata, which we can't use for this purpose in its stdlib flavor until Python 3.10 is the minimum version required).

[dgw]

************* Module sopel_help.managers
sopel_help/managers.py:3:1: W0511: TODO: use stdlib importlib.metadata when possible, after dropping py3.9. (fixme)

pylint doesn't allow the TODO comment, but I think it's important to include the context and future steps. What would you like me to write there instead?

************* Module sopel_help.providers
sopel_help/providers.py:123:4: R0917: Too many positional arguments (7/5) (too-many-positional-arguments)

I didn't touch this, though I think it's a "warning" and not an error.

[Exirel]

@dgw You should be able to rebase on master now and that would fix all the issues with the CI.

[dgw]

Hurrah! Passes CI now.