Start-Stop fixes/cleanup

[kylecarow]

Resolves https://github.nrel.gov/MBAP/fastsim/issues/425

This PR:

• renames stop/start to start-stop
  • start-stop seems to be the standard way to refer to this feature, so let's change the name in FASTSim before this hits the release FASTSim API.
• moves start-stop functions out of the pyo3 api impl, so they are available when pyo3 feature is not active & match other pyo3 api impls
• fixes some issues where start-stop/dfco was not handling thermal soak state freshness, thermal soak for conventional vehicles (surprised this wasnt handled before! maybe thermal soak was only tested for vehicles with a RES)
  • this highlights the need for better test coverage around thermal soak
• move most of common.rs standalone functions into a trait StartStopControl, impl for Conv and HEV start stop controls
• remove VehicleDynamicState helper struct
  • it was a one-off pub struct to organize parameters, makes namespace messy
• rename all instances of engine_on to fc_on throughout
• applies cargo fmt to various files (probably a dupe of changes in other PRs, oh well)

Other notes

• We can apply the dispatching framework for StateMethods that stopstart/dfco have set up to other structs to perhaps simplify the code in mark_non_thermal_fresh and elsewhere

[kylecarow]

@robinsteuteville Assigned you to review this PR - no rush but I would like this to be included before our next release :)