Remove RES and REF typedefs in favor of spelled out Ref<>

These typedefs don't save much typing compared to the full `Ref<Resource>`
and `Ref<RefCounted>`, yet they sometimes introduce confusion among
new contributors.

modules/gdscript/gdscript_editor.cpp

@@ -3106,7 +3106,7 @@ static Error _lookup_symbol_from_base(const GDScriptParser::DataType &p_base, co
 				}
 
 				Variant v;
-				REF v_ref;
+				Ref<RefCounted> v_ref;
 				if (base_type.builtin_type == Variant::OBJECT) {
 					v_ref.instantiate();
 					v = v_ref;