Check windowing mode in CompatUIController#isInDesktopMode()

As CompatUI is built on top of TaskListener, it doesn't
synchronize with shell transitions (thus desktop repo).

Checking desktop eligibility and windowing mode allows to work
this around.

Flag: com.android.window.flags.enable_compat_ui_desktop_mode_synchronization_bugfix
Bug: 436418744
Test: CompatUIControllerTest
Change-Id: Ice106d103278fabf28b7324ea3c7895c531eca67