Improve resource load cache

-Added a new method in Resource: reset_state , used for reloading the same resource from disk
-Added a new cache mode "replace" in ResourceLoader, which reuses existing loaded sub-resources but resets their data from disk (or replaces them if they chaged type)
-Because the correct sub-resource paths are always loaded now, this fixes bugs with subresource folding or subresource ordering when saving.

modules/visual_script/visual_script_flow_control.cpp

@@ -677,6 +677,10 @@ void VisualScriptSwitch::_get_property_list(List<PropertyInfo> *p_list) const {
 	}
 }
 
+void VisualScriptSwitch::reset_state() {
+	case_values.clear();
+}
+
 void VisualScriptSwitch::_bind_methods() {
 }