build!: drop pydantic 1

[tlambert03]

closes #235 and drops support for pydantic v1, pinning to >= 2.8

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.68%. Comparing base (8e94394) to head (52173d0).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #263      +/-   ##
==========================================
- Coverage   99.78%   99.68%   -0.11%     
==========================================
  Files          31       31              
  Lines        1893     1877      -16     
==========================================
- Hits         1889     1871      -18     
- Misses          4        6       +2     

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