### 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/main/java/org/elasticsearch/action/search/SearchResponse.java
}
        @Override
        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
            if (total > 0) {
                builder.startObject(_CLUSTERS_FIELD.getPreferredName());
                builder.field(TOTAL_FIELD.getPreferredName(), total);
                builder.field(SUCCESSFUL_FIELD.getPreferredName(), getClusterStateCount(Cluster.Status.SUCCESSFUL));
                builder.field(SKIPPED_FIELD.getPreferredName(), getClusterStateCount(Cluster.Status.SKIPPED));
                builder.field(RUNNING_FIELD.getPreferredName(), getClusterStateCount(Cluster.Status.RUNNING));
                builder.field(PARTIAL_FIELD.getPreferredName(), getClusterStateCount(Cluster.Status.PARTIAL));
                builder.field(FAILED_FIELD.getPreferredName(), getClusterStateCount(Cluster.Status.FAILED));
                if (clusterInfo.size() > 0) {
                    builder.startObject("details");
                    for (AtomicReference<Cluster> cluster : clusterInfo.values()) {
                        cluster.get().toXContent(builder, params);
                    }
                    builder.endObject();
                }
                builder.endObject();
            }
            return builder;
        }
        public static Clusters fromXContent(XContentParser parser) throws IOException {
            XContentParser.Token token = parser.currentToken();
            ensureExpectedToken(XContentParser.Token.START_OBJECT, token, parser);
            int total = -1;
            int successful = -1;
            int skipped = -1;
            int running = 0;    
            int partial = 0;