Update tiles component repository to remove broadcast

PackageChangeRepository was recently introduced as a centralized place
to listen to package broadcasts. This change migrates the
InstalledTilesComponentRepository to use this new logic instead of
listening to their own broadcast.

Also introduces a convenience state in PackageChangeModel to support a
sensible default value for package changes. This enables the following
pattern: `repository.packageChange(user).onStart { emit(Empty) }` to emit a starting value in the flow

Test: atest InstalledTilesComponentRepositoryImplTest
Flag: NA
Bug: 317059572
Change-Id: Ib0dddc6ea478919cbda5657f546e5d3394235e1d