Modernize actions and re-enable codecov

[timj]

Checklist

• added documentation for a new migration script

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.44%. Comparing base (0da4428) to head (6ecbb74).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #42      +/-   ##
==========================================
- Coverage   58.68%   58.44%   -0.24%     
==========================================
  Files          38       38              
  Lines        1428     1415      -13     
  Branches      302      298       -4     
==========================================
- Hits          838      827      -11     
+ Misses        549      548       -1     
+ Partials       41       40       -1     

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