Add Angle as a backend for rendering

[BeeWarloc]

An work-in-progress PR migrated from the old (closed source) repo.

This commit sets Angle as the default backend used during rendering, however it doesn't change the compositing of the UnoHost. An experiment testing out shared texture between the tool and the UnoHost can be toggled in UnoHostControlImplementation.cs, by setting UseWindowBasedSurface = false. Generally using Angle as a backend feels smoother, and there is less rendering glitches in my experience.

I've applied a "let's get it building again" effort on this after rebasing. When running with UseWindowBasedSurface = true things seem to work. However it seems like I've somehow broken this with UseWindowBasedSurface = false.

This PR includes:

• [ ] Change log
• [ ] Tests