Add Missing NamedWritable Registration for ExecuteEnrichPolicyStatus (elastic#62364)

This was missing and caused nodes to drop out of the cluster on serialization failures
when ever one tried to get an enrich policy task by name.
The test in here is a little dirty but I figured it would be nice to have an actual reproducer
for the issue and I couldn't find any infrastructure to nicely time the tasks so I put this on
top of existing test infra.

Author: original-brownbear

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/XPackClientPlugin.java

@@ -51,6 +51,7 @@
 import org.elasticsearch.xpack.core.enrich.action.ExecuteEnrichPolicyAction;
 import org.elasticsearch.xpack.core.enrich.action.GetEnrichPolicyAction;
 import org.elasticsearch.xpack.core.enrich.action.PutEnrichPolicyAction;
+import org.elasticsearch.xpack.core.enrich.action.ExecuteEnrichPolicyStatus;
 import org.elasticsearch.xpack.core.eql.EqlFeatureSetUsage;
 import org.elasticsearch.xpack.core.flattened.FlattenedFeatureSetUsage;
 import org.elasticsearch.xpack.core.frozen.FrozenIndicesFeatureSetUsage;
@@ -641,7 +642,8 @@ public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
                 new NamedWriteableRegistry.Entry(XPackFeatureSet.Usage.class, XPackField.ANALYTICS, AnalyticsFeatureSetUsage::new),
                 // Enrich
                 new NamedWriteableRegistry.Entry(XPackFeatureSet.Usage.class, XPackField.ENRICH, EnrichFeatureSet.Usage::new),
-                // Searchable snapshots
+                new NamedWriteableRegistry.Entry(Task.Status.class, ExecuteEnrichPolicyStatus.NAME, ExecuteEnrichPolicyStatus::new),
+                    // Searchable snapshots
                 new NamedWriteableRegistry.Entry(XPackFeatureSet.Usage.class, XPackField.SEARCHABLE_SNAPSHOTS,
                     SearchableSnapshotFeatureSetUsage::new),
                 // Data Streams

x-pack/plugin/enrich/src/internalClusterTest/java/org/elasticsearch/xpack/enrich/EnrichMultiNodeIT.java

@@ -6,6 +6,9 @@
 package org.elasticsearch.xpack.enrich;
 
 import org.apache.lucene.search.TotalHits;
+import org.elasticsearch.ResourceNotFoundException;
+import org.elasticsearch.action.ActionFuture;
+import org.elasticsearch.action.admin.cluster.node.tasks.get.GetTaskResponse;
 import org.elasticsearch.action.admin.indices.refresh.RefreshRequest;
 import org.elasticsearch.action.bulk.BulkItemResponse;
 import org.elasticsearch.action.bulk.BulkRequest;
@@ -23,6 +26,7 @@
 import org.elasticsearch.index.reindex.ReindexPlugin;
 import org.elasticsearch.ingest.common.IngestCommonPlugin;
 import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.tasks.TaskInfo;
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.xpack.core.XPackSettings;
 import org.elasticsearch.xpack.core.enrich.EnrichPolicy;
@@ -222,7 +226,27 @@ private static void createAndExecutePolicy() {
         );
         PutEnrichPolicyAction.Request request = new PutEnrichPolicyAction.Request(POLICY_NAME, enrichPolicy);
         client().execute(PutEnrichPolicyAction.INSTANCE, request).actionGet();
-        client().execute(ExecuteEnrichPolicyAction.INSTANCE, new ExecuteEnrichPolicyAction.Request(POLICY_NAME)).actionGet();
+        final ActionFuture<ExecuteEnrichPolicyAction.Response> policyExecuteFuture = client().execute(
+            ExecuteEnrichPolicyAction.INSTANCE,
+            new ExecuteEnrichPolicyAction.Request(POLICY_NAME)
+        );
+        // Make sure we can deserialize enrich policy execution task status
+        final List<TaskInfo> tasks = client().admin()
+            .cluster()
+            .prepareListTasks()
+            .setActions(EnrichPolicyExecutor.TASK_ACTION)
+            .get()
+            .getTasks();
+        // Best effort, sometimes the enrich policy task will not be visible yet or will have already finished
+        if (tasks.isEmpty() == false) {
+            try {
+                final GetTaskResponse getTaskResponse = client().admin().cluster().prepareGetTask(tasks.get(0).getTaskId()).get();
+                assertEquals(getTaskResponse.getTask().getTask().getAction(), EnrichPolicyExecutor.TASK_ACTION);
+            } catch (ResourceNotFoundException e) {
+                // ignored, could be the task has already finished
+            }
+        }
+        policyExecuteFuture.actionGet();
     }
 
     private static void createPipeline() {