Add flux executor support for PsijWorker

[adi611]

Types of changes

• New feature (non-breaking change which adds functionality)

Summary

Adds flux executor support for PsijWorker and a GitHub Actions workflow testflux.yml for testing

Known issues

• jobtap errors: (non-breaking; tests still pass)

jobtap: job.new: callback returned error
jobtap: job.inactive.add: callback returned error

Reference issues flux-framework/flux-core#5475 and flux-framework/flux-core#4991

• test_task.py::test_audit_shellcommandtask_version fails - IndexError: list index out of range

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (0e3d33c) 83.52% compared to head (993c039) 81.82%.

❗ Current head 993c039 differs from pull request most recent head 772d07a. Consider uploading reports for the commit 772d07a to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #710      +/-   ##
==========================================
- Coverage   83.52%   81.82%   -1.71%     
==========================================
  Files          23       23              
  Lines        4990     4990              
  Branches     1429        0    -1429     
==========================================
- Hits         4168     4083      -85     
- Misses        814      907      +93     
+ Partials        8        0       -8     

Flag	Coverage Δ
unittests	81.82% <0.00%> (-1.71%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
pydra/conftest.py	68.62% <ø> (-7.85%)	⬇️
pydra/engine/workers.py	18.31% <0.00%> (-12.15%)	⬇️

... and 4 files with indirect coverage changes

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[adi611]

=========================== short test summary info ============================
FAILED pydra/engine/tests/test_task.py::test_audit_shellcommandtask_version - IndexError: list index out of range
= 1 failed, 1232 passed, 163 skipped, 9 xfailed, 450 warnings in 857.86s (0:14:17) =
Oct 02 18:07:18.412106 broker.err[0]: rc2.0: pytest --psij=flux --color=yes -vs --cov pydra --cov-config .coveragerc --cov-report xml:cov.xml --doctest-modules pydra/ Exited (rc=1) 858.6s

[adi611]

No tests are failing now. Also, I am using psij-python from my fork of the repo here till ExaWorks/psij-python#421 is merged.

[adi611]

I think this is good to go, so I'm removing the WIP tag. Please let me know if I need to make any changes.