Implement the legacy splash screen behavior

For apps opted out of the new splash screen, we show the full background
drawable.
Ensure there has send the splash screen background color to
StartingWindowListener.

Bug: 182880656
Test: manual set useLegacy to true then verify legacy splash screen.
Test: atest WmTests:ActivityRecordTests
Test: atest StartingSurfaceDrawerTests

Change-Id: Icf662f3c5f368f447e718f82f78dc25b909ca9be