lang: interfaces, ast: Add debug methods for graphing scope

This can occasionally help in our debugging of the scope graph.

Co-authored-by: Samuel Gélineau <gelisam@gmail.com>

lang/interfaces/structs.go

@@ -187,3 +187,8 @@ func (obj *ExprAny) Value() (types.Value, error) {
 	}
 	return obj.V, nil
 }
+
+// ScopeGraph adds nodes and vertices to the supplied graph.
+func (obj *ExprAny) ScopeGraph(g *pgraph.Graph) {
+	g.AddVertex(obj)
+}