Clean up activityWindowInfoFlag (2/n)

Remove the function from TaskFragmentOrganizerController.
Move the implementation from SplitController to TaskFragmentOrganizer so
that other implementation of TFOrganizer (system organizer for example)
can still use it to query the status.

Bug: 287582673
Test: atest WMJetpackUnitTests:SplitControllerTest
Flag: EXEMPT refactor for flag cleanup
Change-Id: Ide949b4457e787f6c117be0db463cc1825bb50f7