support Python 3.11, move configs to submodule

[tswast]

I think the top-level configs.py file may cause some packaging problems in general. Moved to the pytest_retry folder where its less likely to conflict with other packages.

Closes #17

[str0zzapreti]

Definitely caused by the location of the configs file rather than anything to do with Python 3.11, I can replicate the issue locally. I would've expected the same error on the new version with pip install -e, but Python... uh, finds a way.

[tswast]

Thanks for the quick review @str0zzapreti

[str0zzapreti]

Sure thing @tswast, thanks for taking the time to make a PR. I never really expected this plugin to get any use outside of my own work, but it's really gratifying to see other people take an interest.