Switch linting from ufmt+usort+flake8+black to Ruff

[akx]

Summary

This PR switches the lint/format stack from ufmt+usort+flake8+black to Ruff.

I converted the Flake8 configuration with flake8-to-ruff, and adjusted it slightly to make reformatting and import sorting do as little as possible.

🤔 Hmm?

Looks like the codegen'd files have DOS file endings, so I had to unix2dos them after re-generating.

Test Plan

1. See what CI says.
2. See what LibCST maintainers say.

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (f8a9b80) 91.09% compared to head (bf9fc4c) 91.09%.

Files	Patch %	Lines
libcst/_parser/conversions/params.py	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1056   +/-   ##
=======================================
  Coverage   91.09%   91.09%           
=======================================
  Files         255      255           
  Lines       26564    26564           
=======================================
  Hits        24198    24198           
  Misses       2366     2366           

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