### 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
}
        public String getClusterAlias() {
            return clusterAlias;
        }
        public String getIndexExpression() {
            return indexExpression;
        }
        public boolean isSkipUnavailable() {
            return skipUnavailable;
        }
        public Status getStatus() {
            return status;
        }
        public boolean isTimedOut() {
            return timedOut;
        }
        public List<ShardSearchFailure> getFailures() {
            return failures;
        }
        public TimeValue getTook() {
            return took;
        }
        public Integer getTotalShards() {
            return totalShards;
        }
        public Integer getSuccessfulShards() {
            return successfulShards;
        }
        public Integer getSkippedShards() {
            return skippedShards;