Update resampled output image's background level and status

[mcara]

Resolves JP-4350

When attempting to resample (again) an already resampled image, the resulting double-resampled image often has an unexplained background offset compared to expected (single-resampled) image. After analysis, this is caused by resample populating most meta of the output resampled image from an input cal image and not updating background-related fields.

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

Regression tests started: https://github.com/spacetelescope/RegressionTests/actions/runs/25517340890 Expect failures due to mismatches in resampled image background value (in meta only) and status (subtracted or not).

[emolter]

I tested locally that manually setting these does fix the background offset issue, so I expect this PR to work too.

Needs regression tests. I would expect some differences.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.38%. Comparing base (e5f2495) to head (cc96c29).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10525   +/-   ##
=======================================
  Coverage   86.38%   86.38%           
=======================================
  Files         373      373           
  Lines       40068    40070    +2     
=======================================
+ Hits        34612    34614    +2     
  Misses       5456     5456           

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[emolter]

I was a little too hasty - this needs regression tests run and probably okified. Not sure how, or if I have the permissions, to dismiss my other review.

The code looks good though to me

[mcara]

@emolter link to the regression tests is at the bottom of the first comment.