chore: Modernize setuptools packaging with pyproject.toml

[rohitsanj]

Summary of changes

• Deprecate and remove setup.py in favor of more modern pyproject.toml -- we continue to use setuptools for packaging.
• Minor doc updates
• Replace flake8 and black with ruff
• Formatted all source files with tox -e format (Enforce single-quoted strings)
• Remove support for end-of-life Python versions 3.6 and 3.7
• Update copyright year to 2024

References:

• https://packaging.python.org/en/latest/guides/modernize-setup-py-project/
• https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/#the-whole-ci-cd-workflow
• https://devguide.python.org/versions/#supported-versions

[rohitsanj]

Ignore the "1 failed deployment" -- I was testing the actions workflow for deploying to testpypi.

[MSeal]

One minor note, our contributing instructions talk about using -e in install but that won't work without a setup.cfg I believe. Otherwise everything worked as expected that I tested out locally.

[rohitsanj]

Thanks for the review.

FWIW, I was able to run pip install -e '.[dev]' without any issues.