chore: Drop Python 3.8 support. Add Python 3.13 support. Update CI/dev dependencies.

[Daverball]

Might also be worth to move the mypy config from setup.cfg to pyproject.toml.

[Daverball]

I don't exactly know what causes it, but for some reason installing flake8-use-pathlib with some of the other updated dependencies breaks a small number tests in 3.12+

I decided to get rid of flake8-use-pathlib and instead use flake8-bugbear for the regression test. It technically should be a more reliable test, since it's a more complex plugin, accessing more nodes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.5%. Comparing base (7621d51) to head (83657c0).
Report is 87 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #197     +/-   ##
=======================================
- Coverage   98.7%   96.5%   -2.2%     
=======================================
  Files          3       3             
  Lines        482     966    +484     
=======================================
+ Hits         476     933    +457     
- Misses         6      33     +27     

Files with missing lines	Coverage Δ
flake8_type_checking/checker.py	96.3% <100.0%> (-2.3%)	⬇️
flake8_type_checking/constants.py	100.0% <ø> (ø)

... and 1 file with indirect coverage changes

[Daverball]

Looks like Codecov was broken for a while due to the outdated action. It just happened to complain loudly in some cases now, where previously it failed silently. The new version seems to work even for tokenless upload with rate limits.

[sondrelg]

Nice! Feel free to move the mypy config too 👍