Merge "Call exitSplitScreen() when user leaves split tasks" into sc-v2-dev am: 2d9741b832 am: 51b92dc3f9

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/15756863

Change-Id: I4d68f214c16c1dcea3c426422571d7e81aef69b0