### 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/TransportSearchAction.java
private final IndexNameExpressionResolver indexNameExpressionResolver;
    private final NamedWriteableRegistry namedWriteableRegistry;
    private final CircuitBreaker circuitBreaker;
    private final ExecutorSelector executorSelector;
    private final int defaultPreFilterShardSize;
    private final boolean ccsCheckCompatibility;
    @Inject
    public TransportSearchAction(
        ThreadPool threadPool,
        CircuitBreakerService circuitBreakerService,
        TransportService transportService,
        SearchService searchService,
        SearchTransportService searchTransportService,
        SearchPhaseController searchPhaseController,
        ClusterService clusterService,
        ActionFilters actionFilters,
        IndexNameExpressionResolver indexNameExpressionResolver,
        NamedWriteableRegistry namedWriteableRegistry,
        ExecutorSelector executorSelector
    ) {
        super(SearchAction.NAME, transportService, actionFilters, (Writeable.Reader<SearchRequest>) SearchRequest::new);
        this.threadPool = threadPool;
        this.circuitBreaker = circuitBreakerService.getBreaker(CircuitBreaker.REQUEST);
        this.searchPhaseController = searchPhaseController;
        this.searchTransportService = searchTransportService;
        this.remoteClusterService = searchTransportService.getRemoteClusterService();
        SearchTransportService.registerRequestHandler(transportService, searchService);
        this.clusterService = clusterService;
        this.transportService = transportService;
        this.searchService = searchService;