SG-41003 Fix case insensitive search in PySide6

[carlos-villavicencio-adsk]

This pull request refactors how case-insensitive regular expressions are created and used for search filtering in both the entity tree and file list forms. The main goal is to ensure compatibility across PySide2 and PySide6 by centralizing the logic for creating the appropriate regex object. This reduces code duplication and addresses issues with case sensitivity handling in different Qt bindings.

[codecov]

Codecov Report

❌ Patch coverage is 69.23077% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 31.86%. Comparing base (a6af1b2) to head (23bf6ca).

Files with missing lines	Patch %	Lines
...tk_multi_workfiles/entity_tree/entity_tree_form.py	0.00%	1 Missing ⚠️
...hon/tk_multi_workfiles/file_list/file_list_form.py	66.66%	1 Missing ⚠️
python/tk_multi_workfiles/file_model.py	66.66%	1 Missing ⚠️
python/tk_multi_workfiles/util.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #166      +/-   ##
==========================================
+ Coverage   31.82%   31.86%   +0.04%     
==========================================
  Files          68       68              
  Lines        7652     7658       +6     
==========================================
+ Hits         2435     2440       +5     
- Misses       5217     5218       +1     

Flag	Coverage Δ
Linux	31.86% <69.23%> (+0.04%)	⬆️
Python-3.10	31.86% <69.23%> (+0.04%)	⬆️
Python-3.11	31.86% <69.23%> (+0.04%)	⬆️
Python-3.9	31.86% <69.23%> (+0.04%)	⬆️
Windows	18.69% <69.23%> (+0.05%)	⬆️
macOS	31.86% <69.23%> (+0.04%)	⬆️

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[julien-lang]

Looks good. Just one comment.

Also, are there any other repositories impacted by the same code?

[julien-lang]

I wonder which way is better between this and assissing the Qt version?!

>>> QtCore.__version__
'6.5.8'

>>> QtCore.__version__
'5.15.3'

[carlos-villavicencio-adsk]

IMO, I think the proposed way is more stable than assuming the Qt version fixed to 5 or 6. Even when we have higher versions, we can still rely on this condition until it gets cleaned by maintenance.