DM-53370: Free resources when no longer needed

[timj]

@andy-slac this is not a complete solution because it looks like all the Engines in Database are never closed.

Checklist

• added documentation for a new migration script
• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

❌ Patch coverage is 49.65035% with 72 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.14%. Comparing base (b4f8fbe) to head (1f2727a).

Files with missing lines	Patch %	Lines
.../lsst/daf/butler_migrate/script/migrate_current.py	0.00%	17 Missing ⚠️
...on/lsst/daf/butler_migrate/script/migrate_stamp.py	38.46%	12 Missing and 4 partials ⚠️
...daf/butler_migrate/script/migrate_set_namespace.py	0.00%	14 Missing ⚠️
...sst/daf/butler_migrate/script/migrate_downgrade.py	50.00%	3 Missing and 3 partials ⚠️
.../lsst/daf/butler_migrate/script/migrate_upgrade.py	50.00%	3 Missing and 3 partials ⚠️
...f/butler_migrate/script/rewrite_sqlite_registry.py	14.28%	6 Missing ⚠️
python/lsst/daf/butler_migrate/database.py	88.00%	3 Missing ⚠️
...t/daf/butler_migrate/script/migrate_dump_schema.py	0.00%	2 Missing ⚠️
...n/lsst/daf/butler_migrate/script/update_day_obs.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #51      +/-   ##
==========================================
+ Coverage   58.95%   59.14%   +0.19%     
==========================================
  Files          40       40              
  Lines        1430     1444      +14     
  Branches      167      168       +1     
==========================================
+ Hits          843      854      +11     
- Misses        552      555       +3     
  Partials       35       35              

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[timj]

I added a Database.close() method and that fixed all the engine leaks.

[timj]

I'm not sure how to deal with the mypy failures. I think that we either have to add ignores and assume that people will run against older butler, or delete the migrations.