Add new code sample for GUIConsole using WinUI 3 - Windows App SDK v1.1

# Description of the new feature/enhancement

I'm creating a WinUI 3 Desktop application (using VS 2022 17.3 **Blank App WinUI 3 in Desktop** template) where I'd like to use the Windows Terminal API to create a terminal window control to use inside my application.

I started by looking at your [GUIConsole.WPF](https://github.com/microsoft/terminal/tree/main/samples/ConPTY/GUIConsole) sample that is written in WPF for .NET Framework 4.6.1.

I tried to port the classes and the XAML window but I'm not able to let it work. I still have errors both on XAML and on code.

# Proposed technical implementation details

Can you please add a new version of the code sample that is written using the new Windows App SDK v1.1?

Start with samples/ConPTY/GUIConsole, the existing WPF sample referenced in the issue, and compare it with the Blank App WinUI 3 in Desktop template. Review the XAML and code errors reported by the author, then define the WinUI 3 Windows App SDK v1.1 sample scope; done means a working GUIConsole sample in that template.

Written by the indexing model from the issue text.