[automerge] Implement splitting from Taskbar long-press 2p: abdf25d226 2p: 5c638fdfbe

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/17530994

Bug: 217964720
Change-Id: I97bc3a9c202ffb6897b66319ae7e0f722f4903cf