JP-3552: use tmp_path instead of tmpdir, enable no:legacypath as a tox factor

[emolter]

Resolves JP-3552

Closes #8311

This PR replaces all instances tmpdir and tmpdir_factory pytest fixtures with tmp_path and tmp_path_factory fixtures, as recommended by pytest (see here), so that these are returning standard pathlib.Path instances instead of legacy py.path.local instances.

Jenkins run here

Checklist for maintainers

• [ ] added entry in CHANGES.rst within the relevant release section
• [ ] updated or added relevant tests
• [ ] updated relevant documentation
• [ ] added relevant milestone
• [ ] added relevant label(s)
• [ ] ran regression tests, post a link to the Jenkins job below. How to run regression tests on a PR
• [ ] Make sure the JIRA ticket is resolved properly

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 55.55556% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 53.21%. Comparing base (4cc0ac1) to head (06b0731). Report is 27 commits behind head on master.

Files	Patch %	Lines
jwst/scripts/okify_regtests.py	0.00%	3 Missing :warning:
jwst/regtest/conftest.py	75.00%	1 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #8327       +/-   ##
===========================================
- Coverage   75.15%   53.21%   -21.95%     
===========================================
  Files         470      389       -81     
  Lines       38604    38463      -141     
===========================================
- Hits        29014    20468     -8546     
- Misses       9590    17995     +8405     

Flag	Coverage Δ
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[hbushouse]

@emolter What's the status of all the suggestions from @jdavies-st ? Do you think they're reasonable?

[emolter]

For some reason, I did not get (or missed) the notification that @jdavies-st reviewed this! Thanks for doing that @jdavies-st, and thanks for the bump @hbushouse. I think the comments are all reasonable and I'll start going through them one by one now.

[jdavies-st]

stpipe.Step parameter validation prevents some file paths being validated when passed pathlib.Path objects. Fine to work around that in this PR. Issue opened here

https://github.com/spacetelescope/stpipe/issues/147

[emolter]

new regtest run started here

[emolter]

Hopefully a final, successful regression test run after fixing two failures: here

edit: all tests ran successfully - jump test failure is unrelated

[emolter]

New regtest run started here.

edit: Regression tests are failing for the two test_nirspec_ifu_spec2 tests where there seemed to be an implicit scope mismatch before. Of course it Works On My Machine^TM so I started this run that only runs tests in that file.

[emolter]

Finally, regression tests for just nirspec_ifu_spec2 passed here. Between this and the previous regtest run, hopefully everything is working now, but I started this new full run just in case.

[hbushouse]

Latest full regtest run has failures that are all unrelated to this PR (they're due to a separate update to datamodels). So this looks good. I'm approving and merging. Nice work everyone - that's a wrap.