Load immersive confirm settings at start

It is necessary to load the settings when the ImmersiveModeConfirmation
started, otherwise the value won't be correct before the first
interaction related to immersive mode and the immersive dialog may
appear unexpectedly.

Bug: 363074067
Test: Enable debug and boot to check the settings value
Flag: com.android.window.flags.system_ui_immersive_confirmation_dialog
Change-Id: Ia7215bbf7f60de9d92dc39a63604c589cfdc1034