migrate tests from nbs to pytest

[deven367]

Description

Checklist:

• This PR has a meaningful title and a clear description.
• The tests pass.
• All linting tasks pass.
• The notebooks are clean.

This PR attempts to remove nbdev from the library, there by removing nbdev and fastcore

cc @goodwanghan

Edit:

• remove nbs folder
• migrate from numpy to google style docstrings
• have a single pyproject.toml instead of setup.py and settings.ini
• remove nbdev related workflows
• minor cosmetic changes wrt linting and code formatting
• add test coverage
• change versioning logic
• update docs

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[codspeed-hq]

CodSpeed Performance Report

Merging #502 will not alter performance

_{Comparing rm-nbdev (5b563ec) with main (f674b45)¹}

🎉 Hooray! pytest-codspeed just leveled up to 4.0.0!

A heads-up, this is a breaking change and it might affect your current performance baseline a bit. But here's the exciting part - it's packed with new, cool features and promises improved result stability 🥳!
Curious about what's new? Visit our releases page to delve into all the awesome details about this new version.

Summary

✅ 12 untouched benchmarks

Footnotes

1. No successful run was found on main (b40a2fa) during the generation of this report, so f674b45 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[CLAassistant]

All committers have signed the CLA.

[goodwanghan]

LGTM

To clarify, we had a lot of offline discussion of the changes, as can be seen from the iterations.