Handle fullscreen app launchs in split init flow for SplitSelectDataHolder

* SystemUi split APIs are overloaded to launch fullscreen tasks
as well, break that out into a separate method for clarity
* Have SplitSelectDataHolder also special case fullscreen launches

Bug: 283045822
Test: Launched various combinations of split tasks,
also tapped on initial view to see fullscreen launch with tasks
and intents
Flag: none

Change-Id: If3de9784b72e0f5f27f1b6d97cbf835b8f5391de