Solver fixes

[rruusu]

These changes are cherry picked from the branch "work", which includes changes originally made to the master branch in October 2024. I hadn't had the time earlier to rebase my code on the major refactoring done to SystemSC.cpp on 19.11.2024 (6d7a397).

Note:

• This request is based on the maintenance/v2.1 branch, on which I have been working on.
• This request includes the changes introduced by #1522 and can be directly merged after it.

Related Issues

• #1326
• #1515
• #1516

Purpose

This change request fixes some issues in simulation of strongly coupled systems. Some calls to FMUs are currently in the wrong order, so that fmi2_completedIntegratorStep() is called before all the inputs have been set to reflect the current state variable values and the time is updated for all components.

This request also adds support for

• Performing events requested by fmi2_completedIntegratorStep() in CVODE.
  • Only adds a TODO comment to doStepEuler().
• Skipping CVODE solver resets for events in which state derivatives are unchanged.

This change enables use of some models from PLECS in a model exchange system.

Approach

Calls to updateInputs() are moved to a time before the call to fmi2_completedIntegratorStep().

Includes some elimination of unnecessary FMI calls for models with no states or event indicators.