Merge "Move OnBackInvoked to BaseActivity." into tm-qpr-dev am: 364af1837e

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/19995367

Change-Id: I2c343441fcc369973d4f487668a070e20e988df4
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>