Move Flyout out of react-native-windows and into a community module

[chrisglein]

This component is added by react-native-windows but we shouldn't be adding anything on top of what's in react-native core. This component should be added via a community module instead.

[BartoszKlonowski]

Blocked by #5539

[rozele]

Blocked by #5539

@BartoszKlonowski This is not technically blocked on the ABIViewManager limitations. Since this is a hoisted component anyway, you can inject a dummy FrameworkElement into the tree with Visibility set to None and attach the Flyout to the appropriate location via other props.

This is, however, blocked on missing public APIs for touch and keyboard event handling.