Add support for Python 3.12, drop support for Python 3.8

[alimanfoo]

• Resolves #512
• Drop support for Python 3.8
• Upgrade actions
• [x] Upgrade protopunica
• [x] Upgrade scikit-allel (https://github.com/cggh/scikit-allel/pull/409)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.79%. Comparing base (637a6ce) to head (3689510). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #514 +/- ## ========================================== + Coverage 98.77% 98.79% +0.02% ========================================== Files 38 38 Lines 3664 3664 ========================================== + Hits 3619 3620 +1 + Misses 45 44 -1 ```

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