Merge "Center drop target icons in landscape mode." into sc-dev am: 3287dd9fa7 am: f67a8f25aa

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14980961

Change-Id: I906294de168c868d9495f0263f4fdb96b24ee04f