Added LauncherIcon DraggedObject

As part of the migration to the DropTargetManager framework, the missing
LauncherIcon drag object was added. Additionally, the DragZoneFactory
was updated to provide drag zones for the LauncherIcon. The Bubble.Left
and Bubble.Right drag zones were updated to have secondary drop targets
set to the bubble bar location if the bubble bar has no bubbles. Tests
for the DragZoneFactory were added to verify new logic.

Bug: 403363673
Flag: com.android.wm.shell.enable_create_any_bubble
Test: DragZoneFactoryTest, DropTargetManagerTest
Change-Id: I6d3e496f99b696028a6003291429c0c2867d6de7