Refresh desktop display mode on sys decors changes

This CL adds a pipeline to propagate system decors changes from Core to
Shell, and uses it to refresh the desktop display mode which depends on
the availability of sys decors.

Flag: com.android.server.display.feature.flags.enable_display_content_mode_management
Flag: com.android.window.flags.enable_display_windowing_mode_switching
Bug: 375319538
Test: DesktopDisplayEventHandlerTest
Test: ActivityTaskManagerServiceTests
Change-Id: I5a1ff8983db65dd8429f0ccaec0a499b6682f28a