Migrates the Uno Platform E2E sample application from a multi-project
structure to the recommended single-project architecture.
This update consolidates platform-specific heads into the main
`HelloWorld` project and introduces a new `Playground.Module` to
showcase Prism for Uno.WinUI features like regions, dialogs, and modularity
within the streamlined project setup. It also updates the target framework to .NET 10.
Dan Siegel