JP-4275: Store tweaked imaging WCS objects in mosaic for transfer to WFSS spectral images in assign_wcs

[tapastro]

Partially resolves JP-4275

This PR stores mosaic members' WCS objects along with their RA/Dec reference positions in i2d mosaic files. During processing of WFSS dispersed images, the WCS of the reference position closest to the dispersed image position is used in place of a fresh imaging WCS upon which we place the dispersed trace transform.

Tasks

• If you have a specific reviewer in mind, tag them.
• add a build milestone, i.e. Build 12.0 (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 changelog readme for instructions)
    • if your change breaks step-level or public API (as defined in the docs), also add a changes/<PR#>.breaking.rst news fragment
  • 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

[codecov]

Codecov Report

❌ Patch coverage is 42.85714% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.02%. Comparing base (1255ce1) to head (e5b76c4).

Files with missing lines	Patch %	Lines
jwst/assign_wcs/util.py	40.00%	18 Missing ⚠️
jwst/assign_wcs/niriss.py	28.57%	5 Missing ⚠️
jwst/resample/resample_step.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10593      +/-   ##
==========================================
- Coverage   87.86%   86.02%   -1.85%     
==========================================
  Files         372      372              
  Lines       40365    40403      +38     
==========================================
- Hits        35468    34756     -712     
- Misses       4897     5647     +750     

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