Transition away notifications when entering glanceable hub

This change fades away the lockscreen notifications when entering the
glanceable hub. It also allows top edge swipes on the glanceable hub to
open the notification shade.

Bug: 315205216
Bug: 315207481
Test: atest KeyguardRootViewModelTest GlanceableHubContainerControllerTest SharedNotificationContainerViewModelTest
Flag: ACONFIG com.android.systemui.communal_hub DEVELOPMENT
Change-Id: Ic35a4aa8b6bef9a41213f3ef816745575bec4d6a