Deprecate DataModel in favor of JwstDataModel

[emolter]

Closes #581

This PR combines DataModel with JwstDataModel and deprecates DataModel.

In this version the code for JwstDataModel would live at src/stdatamodels/model_base.py but available to be imported as both from stdatamodels import JwstDataModel and from stdatamodels.jwst.datamodels import JwstDataModel. The latter is widely used already.

Requires spacetelescope/jwst#10288 to fix one instance where the pipeline was doing from stdatamodels.jwst.datamodels.model_base import JwstDataModel. This construction would no longer work, but since it's (hopefully) not in wide use that should be ok.

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.36%. Comparing base (4a769a6) to head (4d64a17).
⚠️ Report is 82 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #676      +/-   ##
==========================================
- Coverage   90.44%   90.36%   -0.09%     
==========================================
  Files          99       98       -1     
  Lines        4690     4692       +2     
==========================================
- Hits         4242     4240       -2     
- Misses        448      452       +4     

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[emolter]

@tapastro this is still in the investigation phase. It'd be helpful to get your take on whether we want to do this, i.e., do the benefits (code and docs readability/maintainability, clarity on intended base class for downstream use) outweigh the potential for disrupting people's code downstream that might be using DataModel? Do we need to get additional opinions from the various stakeholders about this?

[emolter]

Perhaps relevant to this PR, LIGER evidently uses DataModel: oirlab/liger_iris_pipeline#101 (comment)