Notify StatusBar and NavBar via onDisplayRemoveSystemDecorations when starting mirroring

In this CL, when the connected display is switched from extended mode to
mirroring mode:
(1) WM sends onDisplayRemoveSystemDecorations() to status bar and nav bar.
(2) Status bar and nav bar then perform similar actions to those
triggered by onDisplayRemoved().

Bug: 352461502
Bug: 374240163
Flag: com.android.server.display.feature.flags.enable_display_content_mode_management
Test: manually (adb shell settings put secure mirror_built_in_display {1|0})
Change-Id: If5ebf4dbf62c37eaa5e9efdf8d7fa35babf6a36b