Merge "Add taskbar stashing feedforward, i.e. hint at upcoming stash/unstash" into sc-v2-dev am: 5eb1045cee

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/15302021

Change-Id: I0451b15ebc56036f3c9321cf835f2b519da833ff