Consider adding support for lifecycle components

[ryanmoelter]

We could add support for lifecycle-aware components by implementing LifecycleOwner in either the Screen or Navigator (or both?). Magellan is designed to make things like ViewModels unnecessary, but it would still be nice to have.

[https://developer.android.com/topic/libraries/architecture/lifecycle](Here are the developer docs) for more details.

We may even consider rebuilding screens on top of that lifecycle. I don't particularly like the API (why annotations?) but it might be worth using for a few reasons:

• It's the google-approved way to handle lifecycles
• Other libraries have lifecycle-aware versions
• They have a working implementation of the state machine (LifecycleRegistry) that we can use