Improved SystemBackdrop sample

[MGGSK]

Made the sample easier to use.

Description

1. Renamed the sample from "System Backdrops (Mica/Acrylic)" to "SystemBackdrop"
2. Changed the sample description
3. Added inheritance to the sample page
4. Added a title bar to the sample window
5. The sample window now has a icon
6. The theme of the sample window can now be changed.
7. The sample windows now have a list of backdrops that can be applied. If the user clicks opens the "MicaBackdrop" sample and clicks "Change Backdrop" the window won't apply Acrylic.
8. Fixed the xaml sample code having c# comments.
9. Fixed the DesktopAcrylicBackdrop sample opening the DesktopAcrylicController window.

Motivation and Context

The old sample has no info about how the materials look like.

How Has This Been Tested?

Manual

Screenshots:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)