Add projected mode check in DesktopDisplayModeCtrl

This CL adds a projected mode check in DesktopDisplayModeController.
If the projected mode is explicitly enabled, we don’t need to switch the
default display’s windowing mode.

Flag: com.android.window.flags.enable_projected_display_desktop_mode
Flag: com.android.window.flags.enable_display_windowing_mode_switching
Bug: 399240355
Test: DesktopDisplayModeControllerTest
Change-Id: I9f8801a237f616847250dcf339b2810ad08ec7b9