Add lock icon to glanceable hub

This change also wraps the hub in a constraint layout, so that we can
reuse the existing keyguard section for lock icon.

Bug: 326060686
Test: atest CommunalViewModelTest
Test: atest GlanceableHubContainerControllerTest
Flag: ACONFIG com.android.systemui.communal_hub TEAMFOOD
Change-Id: I973ded25a754d3e042f901acd620d8d45d8e1d93