Code Maintenance / Simplification

[azriel91]

Some outstanding code clean up:

• Collapse StateTypeRegs into StateTypeReg.

  Previously the serialized types for current state and desired states were different -- current state used State<Logical, Physical>, and desired state used just Logical. This was consolidated in Use single State associated type in item spec #69 and Consolidate logical and physical state in ItemSpec. #70.

• (maybe) Move peace_rt_model_core::params::* to peace_cmd::params

  rt_model_core seems like a catch all crate. Currently params reside in there because they were initially created there, and WorkspaceInitializer from rt_model_native and rt_model_web have functions to serialize them. Perhaps we don't need the parameters for serialization to be strongly typed.

• (maybe) Differentiate between StateCurrentDiffs and StateSavedDiffs.

  StateDiffs can be computed between StatesDesired - StatesCurrent, or StatesDesired - StatesSaved.

  If Check that StatesSaved matches StatesCurrent before running EnsureCmd::exec / CleanCmd::exec #86 is implemented, perhaps we don't have to do this.

[azriel91]

Closing: remaining work hasn't been something impeding development for considerable duration.