Rework resizers

[erri120]

Resolves #791

This PR rewrites the resizer code to make it more robust and to follow the Figma design.

[codecov-commenter]

Codecov Report

Attention: 79 lines in your changes are missing coverage. Please review.

Comparison is base (2f65741) 60.25% compared to head (23b86d8) 60.36%.
Report is 1 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #839      +/-   ##
==========================================
+ Coverage   60.25%   60.36%   +0.11%     
==========================================
  Files         594      594              
  Lines       18130    18224      +94     
  Branches     1372     1412      +40     
==========================================
+ Hits        10924    11001      +77     
- Misses       6885     6890       +5     
- Partials      321      333      +12     

Flag	Coverage Δ
Linux	59.72% <65.19%> (+0.13%)	⬆️
Windows	59.60% <65.19%> (+0.15%)	⬆️
clean_environment_tests	60.35% <65.19%> (+0.11%)	⬆️
network_tests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...sMods.App.UI/WorkspaceSystem/WorkspaceGridState.cs	61.98% <ø> (ø)
src/NexusMods.App.UI/WorkspaceSystem/MathUtils.cs	88.67% <69.23%> (-5.67%)	⬇️
...NexusMods.App.UI/WorkspaceSystem/PanelGridState.cs	80.95% <63.63%> (-19.05%)	⬇️
...kspaceSystem/PanelResizer/PanelResizerViewModel.cs	0.00% <0.00%> (ø)
...UI/WorkspaceSystem/Workspace/WorkspaceViewModel.cs	0.00% <0.00%> (ø)
src/NexusMods.App.UI/WorkspaceSystem/GridUtils.cs	90.04% <82.50%> (-5.48%)	⬇️

... and 47 files with indirect coverage changes