Merge "Use the LayoutManager as the source of truth for visible positions" into sc-dev am: 5cc44eb73e am: f492620c7d am: 80d0956b75

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14800536

Change-Id: I37b1f0f0c77f8a67f665aecb93471996afa8b5c4