[WIP] feat: Title bar customization

[MartinZikmund]

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🤖 Generated by Copilot at 9ed0b36

This pull request adds partial support for the new WinUI 3 APIs for customizing the app view, app window, and status bar title bars, using the Microsoft.UI.Windowing namespace. It also updates the TitleBarColorTests user control to demonstrate the usage of these APIs on different platforms. It refactors the code for the StatusBar and ApplicationViewTitleBar classes to use helper classes for managing the platform-specific logic for setting the title bar colors. It adds new files for the AppWindow, AppWindowTitleBar, StatusBarHelper, and TitleBarHelper classes, and modifies some existing files for the Color, ApplicationViewTitleBar, and StatusBar structs and classes.

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