Darken TabControl in dark mode

[willibrandon]

Fixes #11953

Proposed changes

• Style TabControl and make it dark in Dark mode.

Customer Impact

• Fixes an issue with TabControl not being dark enough in Dark mode.

Regression?

• No

Risk

• I believe the risk is low.

Screenshots

Before

After

Test methodology

• Manually tested via scratch project.

Test environment(s)

.NET SDK:
 Version:           9.0.100
 Commit:            59db016f11
 Workload version:  9.0.100-manifests.c6f19616
 MSBuild version:   17.12.7+5b8665660

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.26120
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\9.0.100\

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 75.71412%. Comparing base (237d294) to head (ff8cd62).
Report is 145 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #12471         +/-   ##
===================================================
- Coverage   75.71876%   75.71412%   -0.00465%     
===================================================
  Files           3152        3152                 
  Lines         635709      635715          +6     
  Branches       46970       46971          +1     
===================================================
- Hits          481351      481326         -25     
- Misses        150927      150944         +17     
- Partials        3431        3445         +14     

Flag	Coverage Δ
Debug	75.71412% <0.00000%> (-0.00465%)	⬇️
integration	18.26307% <0.00000%> (-0.00746%)	⬇️
production	49.27047% <0.00000%> (-0.01020%)	⬇️
test	97.05059% <ø> (+0.00028%)	⬆️
unit	46.25161% <0.00000%> (+0.01839%)	⬆️

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[willibrandon]

This is not an area I specialize in and could use some guidance. My plan is to help tackle the remaining dark mode help wanted issues if this approach is acceptable. I have done my best to glean from the work that has already been done and have been experimenting with the dark mode themes that I see in .msstyles.

Am I correct that in an ideal world these controls would not require this additional styling?

[xPaw]

These are also tackled in #11985

[willibrandon]

These are also tackled in #11985

To me it looks like that PR could be the start of a new API proposal. In this PR, my goal is to fix the issue without introducing any new public APIs.