Use navigation with fewer serializable / parcelable objects as arguments

Navigation arguments should be small and simple, like ints and strings and enums. Anything more complex that needs to be passed to a new fragment should either be stored in a shared viewmodel or have its ID passed to the new fragment, and that fragment can retrieve the data from a repository. The latter method should be preferred when we already have IDs, like for tracks. For things like TimeSlots, we'll have to send the show IDs or keep the TimeSlot in `SharedViewModel`.