Merge "Revert "Revert "Use new onStartSplitLegacy when starting split f..."" into tm-dev am: 38ebd4b41c am: f8b78b481a

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/17944715

Change-Id: I38db34a5405f1b45d583d9f6c20472d1b19a9b14
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>