[ResponseOps][Alerting] ES query rule DSL editor doesn't update when you copy/paste a query (#162330)

Resolves https://github.com/elastic/kibana/issues/161595


## Summary

Captures changes in the editor when copying/pasting in values.


### To verify

- Create a new Es Query rule using DSL
- Paste runtime mappings in your query and don't type anything else in
the editor
- Verify that the runtime fields are listed in the group by or aggregate
over options below the query

x-pack/plugins/stack_alerts/public/rule_types/es_query/expression/es_query_expression.tsx

@@ -114,10 +114,10 @@ export const EsQueryExpression: React.FC<
     setCombinedFields(sortBy(currentEsFields.concat(runtimeFields), 'name'));
   };
 
-  const getRuntimeFields = () => {
+  const getRuntimeFields = (xjson: string) => {
     let runtimeMappings;
     try {
-      runtimeMappings = get(JSON.parse(xJson), 'runtime_mappings');
+      runtimeMappings = get(JSON.parse(xjson), 'runtime_mappings');
     } catch (e) {
       // ignore error
     }
@@ -270,7 +270,7 @@ export const EsQueryExpression: React.FC<
           onChange={(xjson: string) => {
             setXJson(xjson);
             setParam('esQuery', convertToJson(xjson));
-            getRuntimeFields();
+            getRuntimeFields(xjson);
           }}
           options={{
             ariaLabel: i18n.translate('xpack.stackAlerts.esQuery.ui.queryEditor', {