[release/10.0] Fix 13829 Dark Mode: Button ForeColor ignored in Dark Mode when FlatStyle is Flat/Popup and Form.ForeColor Is set

[Epica3055]

/backport PR13834 to release/10.0

Fixes #13829

Proposed changes

• Remove BackColorSet, ForeColorSet. use DefaultForeColor,DefaultBackColor to decide whether we should use ButtonBase.BackColor or ButtonBase.ForeColor

Screenshots

After

Test methodology

• manual

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

❌ Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.91947%. Comparing base (bff8288) to head (3c849e0).
⚠️ Report is 4 commits behind head on release/10.0.

❗ There is a different number of reports uploaded between BASE (bff8288) and HEAD (3c849e0). Click for more details.

HEAD has 2 uploads less than BASE

Flag	BASE (bff8288)	HEAD (3c849e0)
Debug	3	2
test	1	0

Additional details and impacted files

@@                   Coverage Diff                   @@
##           release/10.0      #13864          +/-   ##
=======================================================
- Coverage      77.09771%   51.91947%   -25.17825%     
=======================================================
  Files              3273        2064        -1209     
  Lines            644931      287892      -357039     
  Branches          47692       42109        -5583     
=======================================================
- Hits             497227      149472      -347755     
+ Misses           144031      135531        -8500     
+ Partials           3673        2889         -784     

Flag	Coverage Δ
Debug	51.91947% <0.00000%> (-25.17825%)	⬇️
integration	18.98592% <0.00000%> (+0.00049%)	⬆️
production	51.91947% <0.00000%> (+0.01296%)	⬆️
test	?
unit	49.34072% <0.00000%> (+0.01627%)	⬆️

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[LeafShi1]

This change will be in .net11