getModelInstance only dumps the evaluated bindings for structural parameters

[perost]

Description

getModelInstance does not have access to the original bindings of structural parameters, only the evaluated ones.

Steps to Reproduce

Call getModelInstance on a model such as this:

model M
  parameter String controller = "Torque";
  Real x if controlMode == 1;
protected
  parameter Integer controlMode = if controller == "Torque" then 1 else -1;
end M;

The binding for controlModel will only be 1 instead of the original binding.

Expected Behavior

The binding for controlModel should be the whole original if-expression, so that e.g. OMEdit can reevaluate it when the user changes the value of controller.

Additional Context

We currently overwrite the original binding expression when we evaluate a binding, and we also keep track of whether a binding is unevaluated, being evaluated, or is evaluated. This could potentially be changed to instead store the evaluated expression as an optional value in the binding.