Merge "Add taskbar stashing feedforward, i.e. hint at upcoming stash/unstash" into sc-v2-dev am: 5eb1045cee am: 965a9c9b35

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

Change-Id: I27a93f8c244d2d95ccc5aa86b7bd3cbc48cdee03