Deterministic order of event assignments

Ensure event assignments targets are processed in deterministic order.
Otherwise the ordering of state variables may change between subsequent
model imports, which we'd like to avoid.

Closes AMICI-dev#2241.

python/sdist/amici/sbml_import.py

@@ -2776,15 +2776,17 @@ def replace_logx(math_str: Union[str, float, None]) -> Union[str, float, None]:
     return re.sub(r"(^|\W)log(\d+)\(", r"\g<1>1/ln(\2)*ln(", math_str)
 
 
-def _collect_event_assignment_parameter_targets(sbml_model: sbml.Model):
-    targets = set()
+def _collect_event_assignment_parameter_targets(
+    sbml_model: sbml.Model,
+) -> list[sp.Symbol]:
+    targets = []
     sbml_parameters = sbml_model.getListOfParameters()
     sbml_parameter_ids = [p.getId() for p in sbml_parameters]
     for event in sbml_model.getListOfEvents():
         for event_assignment in event.getListOfEventAssignments():
             target_id = event_assignment.getVariable()
             if target_id in sbml_parameter_ids:
-                targets.add(
+                targets.append(
                     _get_identifier_symbol(
                         sbml_parameters[sbml_parameter_ids.index(target_id)]
                     )