Move DragAndDropController to the handheld WMShellModule

- It's only used by other handheld features (split/bubbles/desktop)
  and lets us remove the config_enableShellDragDrop resource down
  the line

Bug: 320797628
Test: Builds
Test: atest NexusLauncherTests
Change-Id: I7dd4f1d1de10a287c951ad9310c4ab40e239d227