Back-port DarkMode Fixes to Preview 6.

[KlausLoeffelmann]

This PR cherry-picks a series of Darkmode fixes from the main branch to the Preview 6 branch.

Microsoft Reviewers: Open in CodeFlow

[merriemcgaw]

thanks @KlausLoeffelmann

[merriemcgaw]

❤️

[codecov]

Codecov Report

Attention: Patch coverage is 22.36543% with 1024 lines in your changes missing coverage. Please review.

Project coverage is 76.50064%. Comparing base (380e851) to head (ee3d8e3).
Report is 8 commits behind head on release/10.0-preview6.

Additional details and impacted files

@@                       Coverage Diff                       @@
##           release/10.0-preview6      #13611         +/-   ##
===============================================================
- Coverage               76.60904%   76.50064%   -0.10840%     
===============================================================
  Files                       3236        3246         +10     
  Lines                     639448      640511       +1063     
  Branches                   47318       47422        +104     
===============================================================
+ Hits                      489875      489995        +120     
- Misses                    146048      146985        +937     
- Partials                    3525        3531          +6     

Flag	Coverage Δ
Debug	76.50064% <22.36543%> (-0.10840%)	⬇️
integration	18.48086% <9.40106%> (-0.04471%)	⬇️
production	50.86361% <22.36543%> (-0.15031%)	⬇️
test	97.41244% <ø> (-0.00039%)	⬇️
unit	48.27243% <21.98635%> (-0.14931%)	⬇️

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