Ensure we're transitioning to GONE when the going away animation starts.

WM starts the going away animation on its own if an activity requests to dismiss the lockscreen (either from the Activity code, or with activity options flags).

In this case, the app/launcher surface *will* become visible, so we should have KTF transition to GONE.

Also, add a "reason" param to startDismissKeyguardTransition to help with debugging bugreports.

Bug: 278086361
Test: atest SystemUITests
Flag: ACONFIG com.android.systemui.keyguard_wm_state_refactor DEVELOPMENT
Change-Id: Ib9e29e68d653908993042a45d75b9612f1da73b4