KeyguardBottomAreaView new impl. - domain layer

- In this second CL in the series, we create the domain layer that will power
the new implementation of KeyguardBottomAreaView
- On its own, this CL doesn't do anything and nothing is using it
- The domain layer contains both the use-cases and models for them
- Use-cases serve as reusable pieces of business logic
- Most use-cases are trivial

Bug: 235403546
Test: Unit tests are included for non-trivial use-cases only. Also manually verified that the bottom area behaves as expected once the
entire CL chain is compiled together

Change-Id: I21434e24f562d7f974ac32e7b72284b2b9c3051f