Speed up filtering

[manuelma]

Makes filtering fast in db editor.

Checklist before merging

• Documentation is up-to-date
• Release notes have been updated
• Unit tests have been added/updated accordingly
• Code has been formatted by black
• Unit tests pass

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (1adf9d5) 63.53% compared to head (d8b7c19) 63.48%.
Report is 2 commits behind head on 0.8-dev.

Files	Patch %	Lines
...lbox/spine_db_editor/widgets/stacked_view_mixin.py	66.66%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##           0.8-dev    #2569      +/-   ##
===========================================
- Coverage    63.53%   63.48%   -0.05%     
===========================================
  Files          196      196              
  Lines        35848    35792      -56     
  Branches      6088     6074      -14     
===========================================
- Hits         22775    22724      -51     
+ Misses       11874    11868       -6     
- Partials      1199     1200       +1     

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