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

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

Change-Id: I6b9e5b3887ccf8cf075b4408e76e3fd510db6e19
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>