Unify Assets for Sample Apps

[hawkerm]

Split off from #444

Description

Splits the initial commits from #444 of moving the assets to the shared project between the UWP and WinUI 3 sample apps.

(Also fixes the WinUI 3 taskbar title of the app in MainWindow.xaml.)

[Sergio0694]

Thank you! Two things:

1. Could you drop the second commit?
2. When opening this branch, I'm seeing this warning:

"The file '..\ComputeSharp.SwapChain\Textures\RustyMetal.png' could not be added to the project. '..\ComputeSharp.SwapChain\Textures\RustyMetal.png' is not an absolute path." [ComputeSharp.SwapChain.Uwp]

Is there a chance to fix this? Is this due to some content file being configured incorrectly?
It's not present in main, so it seems to be caused by the changes in this branch 🤔

Thank you!

[Sergio0694]

Closing this, same as #444 🙂