### 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 (Cluster.STATUS_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                        status = parser.text();
                    } else if (TIMED_OUT.match(currentFieldName, parser.getDeprecationHandler())) {
                        timedOut = parser.booleanValue();
                    } else if (TOOK.match(currentFieldName, parser.getDeprecationHandler())) {
                        took = parser.longValue();
                    } else {
                        parser.skipChildren();
                    }
                } else if (RestActions._SHARDS_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    while ((token = parser.nextToken()) != Token.END_OBJECT) {
                        if (token == Token.FIELD_NAME) {
                            currentFieldName = parser.currentName();
                        } else if (token.isValue()) {
                            if (RestActions.FAILED_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                                failedShards = parser.intValue();
                            } else if (RestActions.SUCCESSFUL_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                                successfulShards = parser.intValue();
                            } 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 {
                            parser.skipChildren();
                        }
                    }
                } else if (token == Token.START_ARRAY) {