"shard started" should show index and shard ID (#25157)

When the cluster state is updated with Shard Started entries, it simply adds "shard-started" as the source of the change.

This adds the index name and shard ID so that we can see who/what is spamming the changes when the index creation step has already left the cluster state.

core/src/main/java/org/elasticsearch/cluster/action/shard/ShardStateAction.java

@@ -375,7 +375,7 @@ public class ShardStateAction extends AbstractComponent {
         public void messageReceived(ShardEntry request, TransportChannel channel) throws Exception {
             logger.debug("{} received shard started for [{}]", request.shardId, request);
             clusterService.submitStateUpdateTask(
-                "shard-started",
+                "shard-started " + request,
                 request,
                 ClusterStateTaskConfig.build(Priority.URGENT),
                 shardStartedClusterStateTaskExecutor,