Clean up TransportRemoteClusterStatsAction (elastic#117119)

No need to have an `ActionType<>` here since we never register this as
an action the `Client` can invoke. Also no need to use a dummy
constructor parameter just to trick the injector into instantiating it,
we can instantiate it ourselves like we do with all other subsidiary
transport-only actions. Also fixes the parent task so the remote action
is a child of the local action rather than a sibling.

Author: DaveCTurner

server/src/main/java/org/elasticsearch/action/admin/cluster/stats/ClusterStatsRequest.java

@@ -48,9 +48,10 @@ public Task createTask(long id, String type, String action, TaskId parentTaskId,
         return new CancellableTask(id, type, action, "", parentTaskId, headers);
     }
 
-    public ClusterStatsRequest asRemoteStats() {
-        this.remoteStats = true;
-        return this;
+    public static ClusterStatsRequest newRemoteClusterStatsRequest() {
+        final var request = new ClusterStatsRequest();
+        request.remoteStats = true;
+        return request;
     }
 
     /**

server/src/main/java/org/elasticsearch/action/admin/cluster/stats/TransportClusterStatsAction.java

@@ -28,6 +28,7 @@
 import org.elasticsearch.action.support.RefCountingListener;
 import org.elasticsearch.action.support.SubscribableListener;
 import org.elasticsearch.action.support.nodes.TransportNodesAction;
+import org.elasticsearch.client.internal.Client;
 import org.elasticsearch.cluster.ClusterSnapshotStats;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.health.ClusterHealthStatus;
@@ -111,20 +112,19 @@ public class TransportClusterStatsAction extends TransportNodesAction<
     private final MetadataStatsCache<MappingStats> mappingStatsCache;
     private final MetadataStatsCache<AnalysisStats> analysisStatsCache;
     private final RemoteClusterService remoteClusterService;
-    private final TransportRemoteClusterStatsAction remoteClusterStatsAction;
 
     @Inject
     public TransportClusterStatsAction(
         ThreadPool threadPool,
         ClusterService clusterService,
         TransportService transportService,
+        Client client,
         NodeService nodeService,
         IndicesService indicesService,
         RepositoriesService repositoriesService,
         UsageService usageService,
         ActionFilters actionFilters,
-        Settings settings,
-        TransportRemoteClusterStatsAction remoteClusterStatsAction
+        Settings settings
     ) {
         super(
             TYPE.name(),
@@ -144,7 +144,9 @@ public TransportClusterStatsAction(
         this.analysisStatsCache = new MetadataStatsCache<>(threadPool.getThreadContext(), AnalysisStats::of);
         this.remoteClusterService = transportService.getRemoteClusterService();
         this.settings = settings;
-        this.remoteClusterStatsAction = remoteClusterStatsAction;
+
+        // register remote-cluster action with transport service only and not as a local-node Action that the Client can invoke
+        new TransportRemoteClusterStatsAction(client, transportService, actionFilters);
     }
 
     @Override

server/src/main/java/org/elasticsearch/action/admin/cluster/stats/TransportRemoteClusterStatsAction.java

@@ -10,11 +10,11 @@
 package org.elasticsearch.action.admin.cluster.stats;
 
 import org.elasticsearch.action.ActionListener;
-import org.elasticsearch.action.ActionType;
 import org.elasticsearch.action.RemoteClusterActionType;
 import org.elasticsearch.action.support.ActionFilters;
 import org.elasticsearch.action.support.HandledTransportAction;
-import org.elasticsearch.client.internal.node.NodeClient;
+import org.elasticsearch.client.internal.Client;
+import org.elasticsearch.client.internal.ParentTaskAssigningClient;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.injection.guice.Inject;
 import org.elasticsearch.tasks.Task;
@@ -27,26 +27,26 @@
 public class TransportRemoteClusterStatsAction extends HandledTransportAction<RemoteClusterStatsRequest, RemoteClusterStatsResponse> {
 
     public static final String NAME = "cluster:monitor/stats/remote";
-    public static final ActionType<RemoteClusterStatsResponse> TYPE = new ActionType<>(NAME);
     public static final RemoteClusterActionType<RemoteClusterStatsResponse> REMOTE_TYPE = new RemoteClusterActionType<>(
         NAME,
         RemoteClusterStatsResponse::new
     );
-    private final NodeClient client;
+
+    private final Client client;
+    private final TransportService transportService;
 
     @Inject
-    public TransportRemoteClusterStatsAction(NodeClient client, TransportService transportService, ActionFilters actionFilters) {
+    public TransportRemoteClusterStatsAction(Client client, TransportService transportService, ActionFilters actionFilters) {
         super(NAME, transportService, actionFilters, RemoteClusterStatsRequest::new, EsExecutors.DIRECT_EXECUTOR_SERVICE);
         this.client = client;
+        this.transportService = transportService;
     }
 
     @Override
     protected void doExecute(Task task, RemoteClusterStatsRequest request, ActionListener<RemoteClusterStatsResponse> listener) {
-        ClusterStatsRequest subRequest = new ClusterStatsRequest().asRemoteStats();
-        subRequest.setParentTask(request.getParentTask());
-        client.execute(
+        new ParentTaskAssigningClient(client, transportService.getLocalNode(), task).execute(
             TransportClusterStatsAction.TYPE,
-            subRequest,
+            ClusterStatsRequest.newRemoteClusterStatsRequest(),
             listener.map(
                 clusterStatsResponse -> new RemoteClusterStatsResponse(
                     clusterStatsResponse.getClusterUUID(),