Explore: Revert QueryRows refactor (#24444)

While query fields should not rely on getting unmounted when the data source changes (and instead react to that change in e.g. componentDidUpdate()), query fields other than PromQueryField still rely on this.

public/app/features/explore/QueryRows.tsx

@@ -20,8 +20,8 @@ export default class QueryRows extends PureComponent<QueryRowsProps> {
     const { className = '', exploreEvents, exploreId, queryKeys } = this.props;
     return (
       <div className={className}>
-        {queryKeys.map((_, index) => {
-          return <QueryRow key={index} exploreEvents={exploreEvents} exploreId={exploreId} index={index} />;
+        {queryKeys.map((key, index) => {
+          return <QueryRow key={key} exploreEvents={exploreEvents} exploreId={exploreId} index={index} />;
         })}
       </div>
     );

public/app/features/explore/state/reducers.ts

@@ -302,6 +302,7 @@ export const itemReducer = (state: ExploreItemState = makeExploreItemState(), ac
       latency: 0,
       queryResponse: createEmptyQueryResponse(),
       loading: false,
+      queryKeys: [],
       supportedModes,
       mode: mode ?? newMode,
       originPanelId: state.urlState && state.urlState.originPanelId,