GroupBuilder: fix query kwarg and add tests

[rkingsbury]

Summary

GroupBuilder has a query kwarg that is supposed to provide filtering of items from the source store, but it does not function correctly and has not been tested.

This PR implements the intended functionality of query and adds tests for it.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.84%. Comparing base (216f1a6) to head (c1ef139).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/maggma/builders/group_builder.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1002   +/-   ##
=======================================
  Coverage   88.84%   88.84%           
=======================================
  Files          46       46           
  Lines        3989     3989           
=======================================
  Hits         3544     3544           
  Misses        445      445           

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