Merge "Adding support for extending back behavior in Launcher" into tm-dev am: a2929870

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/18187213



Change-Id: Id250eb2658fe02126a6bf3ab24758b85b2034d2c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>