Merge "Expose the LauncherModel ModelDelegate" into sc-dev am: 3f504dcbf9 am: 13a94fe310

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14174076

Change-Id: I2a9eed83ab1c100ae53725e603eb78014b4ce1eb