JP-3710: add channel to apcorr table for MIRI LRS and imaging

[emolter]

Resolves JP-3710

Closes spacetelescope/jwst#8715

This PR adds CHANNEL to the MIRI LRS and imaging apcorr datamodels. This will likely always be set to N/A, but its inclusion avoids CRDS errors since CRDS lumps these modes in with MIRI MRS, for which CHANNEL is needed.

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 78.20%. Comparing base (788f7bd) to head (470e0b0).
Report is 7 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #374       +/-   ##
===========================================
+ Coverage   67.59%   78.20%   +10.60%     
===========================================
  Files         115      115               
  Lines        5932     5135      -797     
===========================================
+ Hits         4010     4016        +6     
+ Misses       1922     1119      -803     

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[emolter]

started jwst regtests here https://github.com/spacetelescope/RegressionTests/actions/runs/12658462594

edit: all passing after re-run

[braingram]

LGTM.