Fix TreeView icons not scaling on high DPI

[LeafShi1]

Fixes #13194

Root Cause

TreeView does not scale its ImageList icons when the DPI changes. The native TreeView control receives the original ImageList with unscaled images, causing icons to appear small relative to scaled text and other UI elements at high DPI.

Proposed changes

• Override RescaleConstantsForDpi in TreeView to handle DPI changes
• Create an internal scaled copy of the user's ImageList when DPI requires scaling
• Update OnHandleCreated to use scaled ImageList when running at high DPI
• Clear scaled ImageList when the user changes the ImageList or when it's recreated
• Properly dispose of scaled ImageList resources

Customer Impact

• Affects users displaying TreeView with ImageList on high DPI displays.

Regression?

• No

Risk

• Minimal

Screenshots

Before

The tree view icons are the same size at 200% and 100% DPI

After

The image will be scaled according to the different DPI settings.

AfterChanges.mp4

Test methodology

• Manually

Test environment(s)

• .net 11.0.0-preview.1.26078.110

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Codecov Report

❌ Patch coverage is 18.64407% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.17468%. Comparing base (768186a) to head (564157a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #14255         +/-   ##
===================================================
- Coverage   77.18286%   77.17468%   -0.00819%     
===================================================
  Files           3279        3279                 
  Lines         645129      645187         +58     
  Branches       47728       47739         +11     
===================================================
- Hits          497929      497921          -8     
- Misses        143511      143569         +58     
- Partials        3689        3697          +8     

Flag	Coverage Δ
Debug	77.17468% <18.64407%> (-0.00819%)	⬇️
integration	18.97973% <1.69492%> (-0.01290%)	⬇️
production	52.04668% <18.64407%> (-0.01327%)	⬇️
test	97.40479% <ø> (ø)
unit	49.50740% <18.64407%> (-0.01173%)	⬇️

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[SimonZhao888]

All LGTM!