Clean up split state when moving split task to bubble

Call into StageCoordinator to clean up split state.

Bug: 396313972
Test: put app A and B into split, while split is open, long press on
  app A icon in taskbar and launch it to bubble from the menu, check
  that app A is shown in a bubble on top of app B that is now in
  fullscreen
Flag: com.android.wm.shell.enable_create_any_bubble
Change-Id: Ib02a42b7ad41056a37a865c8706ac84cf1f7568f