Show lock icon over hub

This is a temporary solution while the lock icon and indication area
aren't being persisted to the hub.

Bug: 326060686
Test: verified the lock icon shows up, and properly updates depending on
lock state
Flag: ACONFIG com.android.systemui.communal_hub STAGING

Change-Id: I4f5ea190589e52159d302c3a54bf1bdcaaf4ce86