feedback-actor: Disable direct scanout during lifetime

We only support feedback-actors, such as DnD-icons, in the compositing
path at the moment.

The approach is similar to how we handle certain shell elements.
Implementations need to ensure no references to the object keep
around longer that necessary.

Arguably this should be replaced by a more robust and implicit actor
hierachy detection in the direct scanout code at some point.

Closes #2470 (closed)