Move widget view creation from ViewModel to Compose

The current flow of the communal hub creates an AppWidgetHostView each
time the widget flow is updated. This view creation logic should live
inside the AndroidView Composable, and only called once on factory.

This change also replaces the CommunalContentUiModel with
CommunalContentModel, which lives in the domain layer.

Test: atest CommunalInteractorTest
Bug: 308148193
Flag: ACONFIG com.android.systemui.communal_hub DEVELOPMENT

Change-Id: I3216a70c82973d75de79247605985a9cc0262c8b