Move split functions from RecentsView to SplitSelectStateController

* Moving things out of RecentsView to avoid
dependency on a non-testable class
* Also helping prevent bloating RecentsView.java

Bug: 266482558
Test: Single Chrome instance in recents. Initiate split
with Chrome from workspace, tap on Chrome again in Taskbar,
ensure no crash.

Change-Id: I99ec704479ffaa860f4d80c2cb9f54182f31f41a