Listen for ongoing updates when communal enabled

This change makes it so that updates for ongoing content (media and
smartspace timers) are listened to as long as communal enabled.
Previously, media updates are always listened to, even when not
applicable. Smartspace updates were only listened to when communal was
showing, leading to delays and unexpected behavior when connections were
closed and reopened.

Test: atest CommunalOngoingContentStartable
Test: atest CommunalSmartspaceRepositoryImplTest
Test: atest CommunalMediaRepositoryImplTest
Bug: 322869039
Flag: com.android.systemui.communal_hub
Change-Id: I10c02d0a1e54d2dddef4f7979cdbee6fd0ba0efe