Add some support for opening SSC models

[WilliamJamieson]

Resolves RCAL-976

Closes #

This PR adds limited support for opening SSC derived asdf files using rdm_open .This is not perfect because there is not an easy way to identify if a model is one of the SSC ones from roman_gdps right now.

Tasks

• Update or add relevant roman_datamodels 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).
  • Start a romancal regression test (https://github.com/spacetelescope/RegressionTests/actions/workflows/romancal.yml) with this branch installed ("git+https://github.com/<fork>/rad@<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

[PaulHuwe]

LGTM

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 97.36%. Comparing base (087a60d) to head (b68f3d7).
Report is 93 commits behind head on main.

Files with missing lines	Patch %	Lines
src/roman_datamodels/datamodels/_utils.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #448      +/-   ##
==========================================
- Coverage   97.56%   97.36%   -0.20%     
==========================================
  Files          30       36       +6     
  Lines        2788     3301     +513     
==========================================
+ Hits         2720     3214     +494     
- Misses         68       87      +19     

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