add ruff, drop black/isort/flynt

[even-even]

Hello
In this PR:

1. add https://github.com/astral-sh/ruff for lint
2. drop black/isort/flynt - this checks contains in ruff
3. run ruff check and format in precommits (from poetry dependencies)
4. fix warnings in code

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.05%. Comparing base (d3740fb) to head (208aa24).
⚠️ Report is 51 commits behind head on master.

Files with missing lines	Patch %	Lines
openapi_schema_validator/_keywords.py	63.63%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #285      +/-   ##
==========================================
+ Coverage   82.50%   86.05%   +3.55%     
==========================================
  Files           6       11       +5     
  Lines         280      509     +229     
  Branches       56       83      +27     
==========================================
+ Hits          231      438     +207     
- Misses         31       43      +12     
- Partials       18       28      +10     

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