Merge "Add content description for taskbar all apps button." into tm-qpr-dev am: 4ef5056be8

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/19995934

Change-Id: Iffcfb1d10b623c5d33626997a2c466be3fdfc0ad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>