Fixed ComboBox style and template

[dipeshmsft]

Fixes #10470 , #10656

Description

In this PR I have restyled the ComboBox style and template to make it more similar to WinUI's style, however the styles are slightly different to make it easier in WPF. Here are the list of few major changes in the PR :

1. Split the control template for ComboBox in two parts : one for normal ComboBox and other for EditableComboBox.
2. Fixed the layout in each of the ComboBox template and matched the height and other parameters to WinUI.
3. Added missing control template triggers to get the correct behavior for different states of controls.
4. Added the correct TextBox style Editable ComboBox and fixed the dropdown button styling.
5. Added the correct resources for ComboBox styles.

Bug Fixes covered in this PR :

• Fixes the chevron icon positioning when ComboBox has custom height.
• Chevron button highlight in PointerOver state in Editable combo box mode.
• Fixes the default height of ComboBox control to 32 px.
• Fixes margins and padding for different sub components of ComboBox.
• Fixes the text selection brush color in ComboBox.
• Fixes triggers for different states of ComboBox.
• Fixes the behavior of ComboBox when it is pressed ( for editable ComboBox )

This is not an exhaustive list.

Customer Impact

Correct style for developers.

Regression

No.

Testing

Local app testing.

Risk

Minimal.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Copilot reviewed 1 out of 8 changed files in this pull request and generated no comments.

Files not reviewed (7)

• src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Theme/Dark.xaml: Language not supported
• src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Theme/HC.xaml: Language not supported
• src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Theme/Light.xaml: Language not supported
• src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Variables.xaml: Language not supported
• src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.Dark.xaml: Language not supported
• src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.HC.xaml: Language not supported
• src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.Light.xaml: Language not supported

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 2.98814%. Comparing base (b9af0a5) to head (79605c0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##               main     #10818   +/-   ##
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  Coverage   2.98814%   2.98814%           
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  Files          3319       3319           
  Lines        664895     664895           
  Branches      74675      74675           
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  Hits          19868      19868           
  Misses       644846     644846           
  Partials        181        181           

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