[NB,C] Save array variables in MAT format (#14922)

* Use number of array + scalar variables for freeModelDataVars
* Use number of array + scalar variables to save mat results using index mapping
* New util functions `lengthName` and `lengthDescription` to work with scalar and array variables.
* New util functions `printArrayName` and `printArrayDescription` to print name and comment for scalar and array variables.
* Update NB test `simpleForLoop.mos` to support array variables.

Author: AnHeuermann

OMCompiler/SimulationRuntime/c/simulation/results/simulation_result.h

@@ -37,7 +37,7 @@
 extern "C" {
 #endif /* cplusplus */
 
-/* A prototype for the simulation result interface. */
+/** Simulation result interface. */
 typedef struct simulation_result {
   const char *filename;
   long numpoints;