Cleanup resample in preparation for refactoring

[braingram]

At the moment consider this a test PR.

It is work towards using the new stcal resample. However during that work:

• unused code was discovered
• bugs were uncovered
• the final result will (likely) change regtest results

To manage these changes I'm toying with the idea of making 3 PRs:

1. Cleanup unused code (no regtest changes)
2. Fix bugs, update tests (no regtest changes)
3. Use stcal resample (likely regtest changes)

Tasks

• request a review from someone specific, to avoid making the maintainers review every PR
• add a build milestone, i.e. 24Q4_B15 (use the latest build if not sure)
• Does this PR change user-facing code / API? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • update or add relevant tests
  • update relevant docstrings and / or docs/ page
  • start a regression test and include a link to the running job (click here for instructions)
    • Do truth files need to be updated ("okified")?
      • after the reviewer has approved these changes, run okify_regtests to update the truth files
• if a JIRA ticket exists, make sure it is resolved properly

news fragment change types...

• changes/<PR#>.general.rst: infrastructure or miscellaneous change
• changes/<PR#>.docs.rst
• changes/<PR#>.stpipe.rst
• changes/<PR#>.associations.rst
• changes/<PR#>.scripts.rst
• changes/<PR#>.mosaic_pipeline.rst
• changes/<PR#>.patch_match.rst

steps

• changes/<PR#>.dq_init.rst
• changes/<PR#>.saturation.rst
• changes/<PR#>.refpix.rst
• changes/<PR#>.linearity.rst
• changes/<PR#>.dark_current.rst
• changes/<PR#>.jump_detection.rst
• changes/<PR#>.ramp_fitting.rst
• changes/<PR#>.assign_wcs.rst
• changes/<PR#>.flatfield.rst
• changes/<PR#>.photom.rst
• changes/<PR#>.flux.rst
• changes/<PR#>.source_detection.rst
• changes/<PR#>.tweakreg.rst
• changes/<PR#>.skymatch.rst
• changes/<PR#>.outlier_detection.rst
• changes/<PR#>.resample.rst
• changes/<PR#>.source_catalog.rst

[codecov]

Codecov Report

Attention: Patch coverage is 92.10526% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.07%. Comparing base (826a972) to head (74bb0cc).

Files with missing lines	Patch %	Lines
romancal/resample/resample_step.py	78.57%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1601      +/-   ##
==========================================
- Coverage   78.16%   78.07%   -0.09%     
==========================================
  Files         116      116              
  Lines        7643     7568      -75     
==========================================
- Hits         5974     5909      -65     
+ Misses       1669     1659      -10     

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