Replace flake8 with ruff

[john-sandall]

Relevant links:

• https://github.com/charliermarsh/ruff
• Compat with flake8 >= 6 wemake-services/flake8-eradicate#269 (see last comments)
• https://www.reddit.com/r/Python/comments/11syxd0/the_ruff_python_linter_is_insanely_good/
• https://community.plone.org/t/drop-black-isort-flake8-and-use-ruff/16413
• https://news.ycombinator.com/item?id=34062974
• https://www.reddit.com/r/Python/comments/x30lcs/github_charliermarshruff_an_extremely_fast_python/
• https://www.reddit.com/r/Python/comments/10lsovt/ruff_a_new_fast_and_correct_python_checkerlinter/
• https://www.reddit.com/r/Python/comments/yzhykq/python_linter_comparison_2022_pylint_vs_pyflakes/

Lots of other good linters etc are referenced in these threads. There may also be other Rust-based CLI tools that are worth investigating as part of this repo.