Refactor handling data launching split screen to separate class

* SplitSelectDataHolder contains logic for knowing how
to launch split, separate from the actual API calls to launch split

Flag: ENABLE_SPLIT_LAUNCH_DATA_REFACTOR
Bug: 279494325
Test: Tested w/ all 6 types of launches noted in
SplitSelectDataHolder#@SplitLaunchType.
Also checked to make sure most-recent running tasks are
still being used where applicable.

Change-Id: I8114f87e9956b100622c80f578e291937ed4eeac