Exclude tests involving adjoint solver from make check

[oskooi]

The four tests involving the adjoint solver (particularly test_adjoint_solver.py) take an unusually long time to complete which tends to slow down the CI. This PR modifies make check to exclude these tests and instead creates a make check-adjoint whicn can be used to run all tests (including those involving the adjoint solver).

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.65%. Comparing base (f29a8c7) to head (34cdcde).
⚠️ Report is 117 commits behind head on master.
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HEAD has 4 uploads less than BASE

Flag	BASE (f29a8c7)	HEAD (34cdcde)
	5	1

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #3181       +/-   ##
===========================================
- Coverage   73.81%   63.65%   -10.16%     
===========================================
  Files          18       18               
  Lines        5423     5454       +31     
===========================================
- Hits         4003     3472      -531     
- Misses       1420     1982      +562     

see 10 files with indirect coverage changes

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[stevengj]

Is there a way to conditionally run this?

And/or run it periodically or upon a trigger?

[stevengj]

Maybe add a workflow for a new action to run make check-adjoint periodically (e.g. once a week), which we can also trigger manually.