Allow dragging split tasks on foldables

Allow dragging from app handle on foldables where desktop is not
available, but app handle is available due to bubble feature.
Converting the task to different windowing modes will be supported by
future cls.

Bug: 388851898
Test: manual, set up apps in split screen, try to drag from handles
Flag: com.android.wm.shell.enable_bubble_to_fullscreen
Change-Id: Ied3512a2f84e6b5b5d1ae2cc7ff6338f50b19319