Hide the Task handle when in Lock Task Mode

If we allow apps to use the handle they can try to use split screen or send the task to Desktop Mode. A new listener was created for LockTask mode so Shell doesn't need to call ATMS and do a Binder call.

Fix: 402431290
Test: LockTaskChangeListenerTest, DesktopModeWindowDecorationTests, TaskStackListenerImplTest
Test: Start Lock Task mode using TestDPC and open a locked app (check bug for steps)
Flag: com.android.window.flags.enable_desktop_windowing_enterprise_bugfix
Change-Id: Ibf4a3a4b50698030d1eb9488f33008b69cc7a938