### Description

From the nodes stats API, we should extract the `thread_pool` stats into their own endpoint. This endpoint can then be non-node-centric, and present a global view of the number of completed, rejected, and failed operations for each of the threadpools in the system.
server/src/test/java/org/elasticsearch/action/admin/cluster/node/stats/NodeStatsTests.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */
package org.elasticsearch.action.admin.cluster.node.stats;
import org.elasticsearch.action.NodeStatsLevel;
import org.elasticsearch.action.admin.indices.stats.CommonStats;
import org.elasticsearch.action.admin.indices.stats.CommonStatsFlags;
import org.elasticsearch.action.admin.indices.stats.IndexShardStats;
import org.elasticsearch.action.admin.indices.stats.ShardStats;
import org.elasticsearch.cluster.coordination.ClusterStateSerializationStats;
import org.elasticsearch.cluster.coordination.PendingClusterStateStats;
import org.elasticsearch.cluster.coordination.PublishClusterStateStats;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.node.TestDiscoveryNode;
import org.elasticsearch.cluster.routing.RecoverySource;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.UnassignedInfo;
import org.elasticsearch.cluster.service.ClusterApplierRecordingService;
import org.elasticsearch.cluster.service.ClusterApplierRecordingService.Stats.Recording;
import org.elasticsearch.cluster.service.ClusterStateUpdateStats;
import org.elasticsearch.common.io.stream.BytesStreamOutput;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.network.HandlingTimeTracker;
import org.elasticsearch.common.util.Maps;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.Tuple;