Force fullscreen when another fullscreen is on desktop-first display

This CL avoids applying desktop-first policy for a new task when another
fullscreen app (not fullscreen-in-desk) is focused on the target
display.

Flag: com.android.window.flags.enable_desktop_first_top_fullscreen_bugfix
Bug: 431066262
Test: DesktopTasksControllerTests
Change-Id: I784b9b8eace2f7a43775e70be63e3748fd5416f0