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

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

Bug: 217964720
Change-Id: Ie8cc35c7ba358782186d5c0a9e9d994dfd8ba9a1