DM-54514: Add obs_info legacy test

[timj]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

❌ Patch coverage is 13.33333% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.46%. Comparing base (574efdc) to head (f80f5a4).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
tests/test_visit_image.py	0.00%	8 Missing ⚠️
python/lsst/images/tests/_checks.py	0.00%	3 Missing ⚠️
python/lsst/images/tests/_roundtrip.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
- Coverage   74.63%   74.46%   -0.18%     
==========================================
  Files          50       50              
  Lines        5240     5252      +12     
==========================================
  Hits         3911     3911              
- Misses       1329     1341      +12     

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