### 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
import org.elasticsearch.xcontent.ToXContent;
import org.elasticsearch.xcontent.XContentFactory;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.BooleanSupplier;
import java.util.function.Function;
import java.util.function.LongSupplier;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
import static org.elasticsearch.action.search.SearchType.DFS_QUERY_THEN_FETCH;
import static org.elasticsearch.action.search.SearchType.QUERY_THEN_FETCH;
import static org.elasticsearch.action.search.TransportSearchHelper.checkCCSVersionCompatibility;
import static org.elasticsearch.search.sort.FieldSortBuilder.hasPrimaryFieldSort;
import static org.elasticsearch.threadpool.ThreadPool.Names.SYSTEM_CRITICAL_READ;
import static org.elasticsearch.threadpool.ThreadPool.Names.SYSTEM_READ;
public class TransportSearchAction extends HandledTransportAction<SearchRequest, SearchResponse> {