chore(ci): Split pre-release tests into cron job

[effigies]

Following what we did in nipy/nibabel#1466.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.83%. Comparing base (3b3cc2d) to head (1f1081f).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #68   +/-   ##
=======================================
  Coverage   76.83%   76.83%           
=======================================
  Files          13       13           
  Lines         846      846           
  Branches      124      124           
=======================================
  Hits          650      650           
  Misses        169      169           
  Partials       27       27           

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