### 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 
x-pack/plugin/async-search/src/internalClusterTest/java/org/elasticsearch/xpack/search/CrossClusterAsyncSearchIT.java
: SearchResponse.Cluster.Status.FAILED;
            assertThat(remoteClusterSearchInfo.getStatus(), equalTo(expectedStatus));
            if (minimizeRoundtrips) {
                assertNull(remoteClusterSearchInfo.getTotalShards());
                assertNull(remoteClusterSearchInfo.getSuccessfulShards());
                assertNull(remoteClusterSearchInfo.getSkippedShards());
                assertNull(remoteClusterSearchInfo.getFailedShards());
                assertThat(remoteClusterSearchInfo.getFailures().size(), equalTo(1));
            } else {
                assertThat(remoteClusterSearchInfo.getTotalShards(), equalTo(remoteNumShards));
                assertThat(remoteClusterSearchInfo.getSuccessfulShards(), equalTo(0));
                assertThat(remoteClusterSearchInfo.getSkippedShards(), equalTo(0));
                assertThat(remoteClusterSearchInfo.getFailedShards(), equalTo(remoteNumShards));
                assertThat(remoteClusterSearchInfo.getFailures().size(), equalTo(remoteNumShards));
            }
            assertNull(remoteClusterSearchInfo.getTook());
            assertFalse(remoteClusterSearchInfo.isTimedOut());
            ShardSearchFailure remoteShardSearchFailure = remoteClusterSearchInfo.getFailures().get(0);
            assertTrue("should have 'index corrupted' in reason", remoteShardSearchFailure.reason().contains("index corrupted"));
        }
        
        {
            AsyncStatusResponse statusResponse = getAsyncStatus(response.getId());
            assertTrue(statusResponse.isPartial());
            SearchResponse.Clusters clusters = statusResponse.getClusters();
            assertThat(clusters.getTotal(), equalTo(2));
            assertThat(clusters.getClusterStateCount(SearchResponse.Cluster.Status.SUCCESSFUL), equalTo(1));
            assertThat(clusters.getClusterStateCount(SearchResponse.Cluster.Status.RUNNING), equalTo(0));
            assertThat(clusters.getClusterStateCount(SearchResponse.Cluster.Status.PARTIAL), equalTo(0));
            if (skipUnavailable) {