Add CommunalHostView to NotificationsQuickSettingsContainer.

CommunalHostView provides a place for communal content to be
shown. This changelist positions the view within the lockscreen
as a child of NotificationsQuickSettingsContainer. The
NotificationPanelViewController is responsible for adjusting the
CommunalHostView layout.

Bug: 193676840
Test: atest SystemUITests
Change-Id: I097c431a47d79d2b300605dbd56c0158e26b0c2f