Show allowlisted widgets in communal hub

- Update the layout library to pass the size information back to the
  composable
- Each AppWidgetHostView updates the provider with the correct size
  information provided above
- Before the local database is set up, the repository unbinds each
  previously bound widget, and rebinds each widget from the allowlist

Test: atest CommunalWidgetRepositoryImplTest
Test: verified widgets showing by following go/enable_glanceable_hub
Bug: 305284915
Fix: 305284915

Change-Id: I50ca3d68538bb4efcb8b6356e96b34a4330df360