[windows] Switch to XAML islands.

[alexmercerind]

Switching to XAML islands on Windows can be a great step towards:

• Improving performance.
• Depending on officially documented APIs.
• Dealing with changes & providing Windows like exposed APIs.
• Allowing to add effect to particular part of the window.
• Removing bitsdojo_window as a dependency.

I'll be trying to do this in future & switch away from SetWindowCompositionAttribute.

[alexmercerind]

I'm still researching on this & created a new repo here to keep the progress.