Refactor 'simulate_schedule`

[j-atkins]

simulate_schedule.py can probably be refactored to base class --> instrument sub-class structure, and dataclasses/Pydantic models moved to the models dir. expedition dir can then be removed.

[j-atkins]

Note, some discussion on this in #249, on how restructuring/refactoring could be used to benefit the interaction between simulate_schedule and Instrument simulations