DM-48094: Fix dataset fields not working in Butler.query_datasets

[dhirving]

Fix an issue where dataset fields like ingest_date were raising InvalidQueryError: Unrecognized identifier because the where clause was being applied before query was known to be a dataset query.

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes
• (if changing dimensions.yaml) make a copy of dimensions.yaml in configs/old_dimensions

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.49%. Comparing base (36ed777) to head (3af7307).
Report is 2 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1133   +/-   ##
=======================================
  Coverage   89.49%   89.49%           
=======================================
  Files         366      366           
  Lines       48801    48805    +4     
  Branches     5900     5900           
=======================================
+ Hits        43676    43680    +4     
  Misses       3718     3718           
  Partials     1407     1407           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.