Until now when a Component without a parent was passed to setOwner() the
ParentVisibilityChangedListener would not install any hooks to any
components, hence it would not be notified, when the owner was added
to a parent.

Until now when a Component without a parent was passed to setOwner() the
ParentVisibilityChangedListener would not install any hooks to any
components, hence it would not be notified, when the owner was added
to a parent.

Also updates the drop shadower so that the DPI-awareness of the shadows
matches the DPI-awareness of the shadowed component.

The issue was caused by DropShadower using the ComponentListener interface
to listen to its target Component's changes and creating shadow Components
only if the target was visible during the event callbacks. However it was
possible that during the events the target was not yet visible because one
of its parents was not visible. When the parent became visible it would not
trigger a callback for the observed child component.

The fix attaches a ComponentListener recursively to all parents starting
from the target and responds to each componentVisibilityChanged() event.