chore: Experiment with running subsets of Comet test suite in parallel

[andygrove]

Which issue does this PR close?

Closes #1800

Rationale for this change

Running subsets of the suite in parallel will help isolate the CI failure and also speed builds uup.

What changes are included in this PR?

How are these changes tested?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.55%. Comparing base (f09f8af) to head (4bbe46a).
⚠️ Report is 832 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1801      +/-   ##
============================================
+ Coverage     56.12%   57.55%   +1.43%     
- Complexity      976     1065      +89     
============================================
  Files           119      128       +9     
  Lines         11743    12443     +700     
  Branches       2251     2346      +95     
============================================
+ Hits           6591     7162     +571     
- Misses         4012     4053      +41     
- Partials       1140     1228      +88     

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