Keyguard Shell Transitions: send keyguard/aod updates to all displays.

We used to delegate this responsibility to ATMS, who iterates through
all the displays and then call on KeyguardController individually. We'll
migrate this iteration to Shell side now so that going forward if it
ever needs to only update a set, it can control that itself.

Bug: 364930619
Test: atest
android.server.wm.multidisplay.MultiDisplayLockedKeyguardTests#testPrivateDisplayHideContentWhenLocked
Test: atest
android.server.wm.multidisplay.MultiDisplayLockedKeyguardTests#testVirtualDisplayHideContentWhenLocked
Test: atest
android.server.wm.multidisplay.MultiDisplayLockedKeyguardTests#testDismissKeyguard_secondaryDisplay
Flag: com.android.window.flags.ensure_keyguard_does_transition_starting

Change-Id: Iad86bd9e092ed53dde678071e5ddeae27426d6d8