### 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
} else if (RestActions.TOTAL_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                                totalShards = parser.intValue();
                            } else if (RestActions.SKIPPED_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                                skippedShards = parser.intValue();
                            } else {
                                parser.skipChildren();
                            }
                        } else if (token == Token.START_ARRAY) {
                            if (RestActions.FAILURES_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                                while ((token = parser.nextToken()) != Token.END_ARRAY) {
                                    failures.add(ShardSearchFailure.fromXContent(parser));
                                }
                            } else {
                                parser.skipChildren();
                            }
                        } else {
                            parser.skipChildren();
                        }
                    }
                } else if (Clusters._CLUSTERS_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    clusters = Clusters.fromXContent(parser);
                } else {
                    parser.skipChildren();
                }
            }
        }
        SearchResponseSections searchResponseSections = new SearchResponseSections(
            hits,
            aggs,
            suggest,