Add miri lrs spec wcs model

[jemorrison]

Helps Resolve JP-3848

This PR replaces #382. There we too many conflicts to resolve easily after the code style changes were made.

Closes #

This PR adds a datamodel of the reference file, specwcs, for MIRI LRS data. It can be used for fixed slit or slitless data. The reference file for fixed slit contains the V2,V3 corners of the slit. These values are not in the slitless reference file and default to None when the reference files are read in using the data models

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 jwst regression tests with this branch installed ("git+https://github.com/<fork>/stdatamodels@<branch>")

news fragment change types...

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.misc.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

Attention: Patch coverage is 53.19149% with 22 lines in your changes missing coverage. Please review.

Project coverage is 77.94%. Comparing base (788f7bd) to head (33a6407).
Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
src/stdatamodels/jwst/datamodels/wcs_ref_models.py	53.19%	22 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #393       +/-   ##
===========================================
+ Coverage   67.59%   77.94%   +10.34%     
===========================================
  Files         115      115               
  Lines        5932     5192      -740     
===========================================
+ Hits         4010     4047       +37     
+ Misses       1922     1145      -777     

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