Shorten cluster state thread pool name (#106274)

The thread pool name is used to report metrics, and
MetricNameValidator enforces a max of 30 characters.

server/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java

@@ -181,7 +181,7 @@ public abstract class BlobStoreRepository extends AbstractLifecycleComponent imp
     public static final String STATELESS_SHARD_READ_THREAD_NAME = "stateless_shard_read";
     public static final String STATELESS_TRANSLOG_THREAD_NAME = "stateless_translog";
     public static final String STATELESS_SHARD_WRITE_THREAD_NAME = "stateless_shard_write";
-    public static final String STATELESS_CLUSTER_STATE_READ_WRITE_THREAD_NAME = "stateless_cluster_state_read_write";
+    public static final String STATELESS_CLUSTER_STATE_READ_WRITE_THREAD_NAME = "stateless_cluster_state";
 
     public static final String SNAPSHOT_PREFIX = "snap-";