[Multi SDFG, Fortran] Make `functionStatementEliminator()` to modify the `node` itself and return it, so that it cannot forget to account for all the members of `node` when constructing a new one. #1769
Introduce explicit constructor for Program_Node, since it allows for better tracking of what are the member variables. We want to do this for all of the ~84 classes in the ast_internal_classes.py, but for now we start with just one.
Additionally:
Program_Node, since it allows for better tracking of what are the member variables. We want to do this for all of the ~84 classes in theast_internal_classes.py, but for now we start with just one.