Always refer to the latest TaskInfo

This CL ensures that the latest TaskInfo is used for the desktop first
policy check.
Currently, the returned TaskInfo of
FocusTransitionObserver#getFocusedTaskOnDisplay is not ensured to have
the up-to-date properties because the observer updates the cached
TaskInfo only when the focus is changed. It only guarantees to have the
proper taskId.

Flag: com.android.window.flags.enable_desktop_first_top_fullscreen_bugfix
Bug: 435258342
Test: DesktopTasksControllerTests
Change-Id: Idc94f562bddb8c193fc511501625a0a99a410cf2