AL-837: Calculate output WCS for resample from already-known s_region

[emolter]

Resolves AL-837

This PR simplifies the calculation of the output WCS for resample. Previously, the wcs_from_footprints function accepted a list of WCS objects, one for each input model, and computed the footprints from those WCS objects to pass into _calculate_new_wcs(). However, computing the footprints here is unnecessary because that information is already stored in the S_REGION keyword. This PR makes wcs_from_footprints take in an actual footprint instead, in the form of either a numpy array or an S_REGION string.

This PR will require small changes to both jwst and romancal, both of which are using the wcs_from_footprints function. I'm not sure there's a way to avoid that. One other non-hidden function changed, compute_fiducial, but this is not used for JWST or Romancal - both repositories have their own copy of a function with that name.

Tasks

• update or add relevant tests
• update relevant docstrings and / or docs/ page
• Does this PR change any API used downstream? (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)
  • run regression tests with this branch installed ("git+https://github.com/<fork>/stcal@<branch>")
    • jwst regression test
    • romancal regression test

news fragment change types...

• changes/<PR#>.apichange.rst: change to public API
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.general.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.24%. Comparing base (60bd3b8) to head (830cf47).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #307      +/-   ##
==========================================
+ Coverage   86.21%   86.24%   +0.02%     
==========================================
  Files          47       49       +2     
  Lines        8812     8838      +26     
==========================================
+ Hits         7597     7622      +25     
- Misses       1215     1216       +1     

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[emolter]

JWST regression tests started here

[emolter]

tracking down JWST regression test failures now

[mairanteodoro]

romancal's issue 1455 needs to be resolved before this PR, since it seems that TweakRegStep is only updating the WCS but not s_region.

[emolter]

@mairanteodoro good to know. When you do update s_region, it might be good to be aware of this comment. The regression test failures for JWST come from the fact that wcs.footprint() and S_REGION differ by half a pixel due to JWST's use of center=True in compute_s_region_imaging()