Dynamically size and order ongoing content

- UMO is dynamically sized based on the number of ongoing content
- Ongoing cards are ordered based on creation time

Test: atest CommunalInteractorTest
Test: atest CommunalMediaRepositoryImplTest
Bug: 318423695
Bug: 311245493
Fix: 311245493
Flag: ACONFIG com.android.systemui.communal_hub DEVELOPMENT
Change-Id: I5d8086e77d42cde7420e17c1a77f3b6cd7c5b7c9