Spec: Restructure the Toolkit

[Lamparter]

📄 Description

This is an incredibly big task and project, and will require a lot of help.
This issue represents and tracks the progress of the brand new Toolkit (new name required!) including the merge of:

• GlowUI
• CrimsonUI
• Crimson.Toolkit
• CubeKit

⚡ API Changes

This will require significant changes to the way that the Toolkit API is built. Unlike CommunityToolkit and others, this will have both UWP and WindowsAppSDK versions inside the same package (using the Alloy application model documented here)

👥 Usage scenarios

A rudimentary list of the most famous new Toolkit APIs: (see sub-issues or comments for more)

UnifiedApp

public partial class UnifiedApp : Microsoft.UI.Xaml.Application

ThemeHelper

public bool IsThemeEnabled(Guid themeId)

🔙 Backward Compatibility

This will break everything that previously used GlowUI, CubeKit, CrimsonUI and Riverside.Toolkit.
They will need to be adapted and namespace references must be updated.

🤔 Difficulty

High