Merge "launcher: create attrs for more horizontal margin options" into sc-v2-dev am: bfb6996484 am: 11f703dd36

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/15879755

Change-Id: Ia344342fa38c7e9a330280a29aa852279779662b