Modern maintenance tooling

[ogrisel]

• Run black and ruff on all files via pre-commit (fixes Use black to format the code base #497),
• Use pyproject.toml (with flit) instead of setup.py for packaging and tool config,
• Update the CI to reuse the pre-commit setup as PR linter.

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (c6f8cd4) 96.07% compared to head (39cae0b) 96.08%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #521      +/-   ##
==========================================
+ Coverage   96.07%   96.08%   +0.01%     
==========================================
  Files           3        3              
  Lines         560      562       +2     
  Branches      116      116              
==========================================
+ Hits          538      540       +2     
  Misses         11       11              
  Partials       11       11              

Files	Coverage Δ
cloudpickle/__init__.py	100.00% <100.00%> (ø)
cloudpickle/cloudpickle_fast.py	100.00% <ø> (ø)
cloudpickle/cloudpickle.py	96.02% <93.61%> (ø)

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[ogrisel]

When merging this PR we should rather rebase and merge (or create a merge commit) to be able to include the black commit in .git-blame-ignore-revs.

[rgbkrk]

Thank you @ogrisel