Clean up the legacy split screen (6/n)

Clean up legacy split screen from remaining classes.

Bug: 199236198
Test: atest ActivityRecordTests ConfigurationContainerTests
            RootWindowContainerTests TaskTests TaskFragmentTest
	    WindowStateTests ActivityStarterTests DisplayContentTests
Change-Id: I0cc2b51e68ae2b8d06a173357ce463e586ec0e85
12 files changed