Add aggregation jobs to maxtrix workflows

[tleonhardt]

This is in preparation for establishing better branch protection rules. In order to make those maintainable, we need these aggregator jobs which aren't tied to specific os or python versions in the matrix.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.66%. Comparing base (a8b362c) to head (f92693a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1747      +/-   ##
==========================================
+ Coverage   99.64%   99.66%   +0.01%     
==========================================
  Files          23       23              
  Lines        5960     5960              
==========================================
+ Hits         5939     5940       +1     
+ Misses         21       20       -1     

Flag	Coverage Δ
unittests	99.66% <ø> (+0.01%)	⬆️

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