Make dict2inst to work with arbitrary _init parameters

This is achieved by skipping initializer call while creating an instance
of a GDScript. This is implemented by passing -1 as an argument count
to `_new` and interpreting any value below 0 to mean that the initializer
should not be called during instantiation, because internal members of
an instance are going to be overridden afterwards.

modules/gdscript/gdscript_functions.cpp

@@ -1197,8 +1197,7 @@ void GDScriptFunctions::call(Function p_func, const Variant **p_args, int p_arg_
 					return;
 				}
 			}
-
-			r_ret = gdscr->_new(nullptr, 0, r_error);
+			r_ret = gdscr->_new(nullptr, -1 /*skip initializer*/, r_error);
 
 			GDScriptInstance *ins = static_cast<GDScriptInstance *>(static_cast<Object *>(r_ret)->get_script_instance());
 			Ref<GDScript> gd_ref = ins->get_script();