Migrate Settings to Desktop WinUI3 application

[crutkas]

Currently this is a XAML Island, WinUI 2.x with a WPF container app shell. Lets migrate this to be a pure desktop solution when the first opportunity comes.

Two primary requirements for WinUI3 to have are

1. Forward compatibility
2. Unpackaged app support (aka PowerToys not being installed as an MSIX)
3. PowerToysInterop needs to stop making FxFramework item and refactored

[crutkas]

Referenced in https://github.com/microsoft/PowerToys/wiki/Roadmap#best-effort-for-stabilization