### Description

`SearchResponse.Clusters` currently uses a `HashMap<String, AtomicReference>` for storing Cluster objects. The AtomicReference CAS swaps are done in a do/while loop in most cases (e.g., in `CCSSingleCoordinatorSearchProgressListener`).

This can be replaced with a `ConcurrentHashMap` in conjunction with either `compute()` method or the `replace(key, assumed_previous_value, value)` method for atomically swapping in a new Cluster object with a CAS operation, assuring that the updates don't lose data from competing threads doing separate Cluster object updates.

See: https://github.com/elastic/elasticsearch/pull/98457/files#r1310467586 
server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterSearchIT.java
assertNull(clusters.getCluster(RemoteClusterAware.LOCAL_CLUSTER_GROUP_KEY));
            SearchResponse.Cluster remoteClusterSearchInfo = clusters.getCluster(REMOTE_CLUSTER).get();
            assertNotNull(remoteClusterSearchInfo);
            SearchResponse.Cluster.Status expectedStatus = skipUnavailable
                ? SearchResponse.Cluster.Status.SKIPPED
                : SearchResponse.Cluster.Status.FAILED;
            assertThat(remoteClusterSearchInfo.getStatus(), equalTo(expectedStatus));
            assertNull(remoteClusterSearchInfo.getTotalShards());
            assertNull(remoteClusterSearchInfo.getSuccessfulShards());
            assertNull(remoteClusterSearchInfo.getSkippedShards());
            assertNull(remoteClusterSearchInfo.getFailedShards());
            assertThat(remoteClusterSearchInfo.getFailures().size(), equalTo(1));
            assertNull(remoteClusterSearchInfo.getTook());
            assertFalse(remoteClusterSearchInfo.isTimedOut());
            ShardSearchFailure remoteShardSearchFailure = remoteClusterSearchInfo.getFailures().get(0);
            assertTrue("should have 'index corrupted' in reason", remoteShardSearchFailure.reason().contains("index corrupted"));
        }
    }
    private static void assertOneFailedShard(SearchResponse.Cluster cluster, int totalShards) {
        assertNotNull(cluster);
        assertThat(cluster.getStatus(), equalTo(SearchResponse.Cluster.Status.PARTIAL));
        assertThat(cluster.getTotalShards(), equalTo(totalShards));
        assertThat(cluster.getSuccessfulShards(), equalTo(totalShards - 1));
        assertThat(cluster.getSkippedShards(), equalTo(0));
        assertThat(cluster.getFailedShards(), equalTo(1));
        assertThat(cluster.getFailures().size(), equalTo(1));
        assertThat(cluster.getTook().millis(), greaterThan(0L));
        ShardSearchFailure remoteShardSearchFailure = cluster.getFailures().get(0);
        assertTrue("should have 'index corrupted' in reason", remoteShardSearchFailure.reason().contains("index corrupted"));
    }