DevMenu sizes wrong, should contain a scrollviewer

[asklar]

If the window is near the top, the popup will only go as far as the top of the screen and as low as the top of the app window

Slightly more room:

[chrisglein]

1. XAML is in charge of the flyout positioning here. Which is half of the problem. Maybe a core XAML bug? Check behavior and potentially open a WinUI bug.
2. Independent of that this should have a scroll viewer for cases where it does get clipped.
3. Should this just be using a regular XAML context menu or something more standard?

[jonthysell]

No longer repros.