### 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/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterSearchIT.java
public void testCCSClusterDetailsWhereAllShardsSkippedInCanMatch() throws Exception {
        Map<String, Object> testClusterInfo = setupTwoClusters();
        String localIndex = (String) testClusterInfo.get("local.index");
        String remoteIndex = (String) testClusterInfo.get("remote.index");
        int localNumShards = (Integer) testClusterInfo.get("local.num_shards");
        int remoteNumShards = (Integer) testClusterInfo.get("remote.num_shards");
        SearchRequest searchRequest = new SearchRequest(localIndex, REMOTE_CLUSTER + ":" + remoteIndex);
        searchRequest.allowPartialSearchResults(false);
        boolean minimizeRoundtrips = randomBoolean();
        searchRequest.setCcsMinimizeRoundtrips(minimizeRoundtrips);
        if (randomBoolean()) {
            searchRequest.setBatchedReduceSize(randomIntBetween(3, 20));
        }
        boolean dfs = randomBoolean();
        if (dfs) {
            searchRequest.searchType(SearchType.DFS_QUERY_THEN_FETCH);
        }
        if (randomBoolean()) {
            searchRequest.setPreFilterShardSize(1);
        }
        searchRequest.setPreFilterShardSize(1);
        RangeQueryBuilder rangeQueryBuilder = new RangeQueryBuilder("@timestamp").from(EARLIEST_TIMESTAMP - 2000)
            .to(EARLIEST_TIMESTAMP - 1000);
        searchRequest.source(new SearchSourceBuilder().query(rangeQueryBuilder).size(10));
        SearchResponse searchResponse = client(LOCAL_CLUSTER).search(searchRequest).get();
        assertNotNull(searchResponse);
        SearchResponse.Clusters clusters = searchResponse.getClusters();
        assertFalse("search cluster results should NOT be marked as partial", clusters.hasPartialResults());
        assertThat(clusters.getTotal(), equalTo(2));
        assertThat(clusters.getClusterStateCount(SearchResponse.Cluster.Status.SUCCESSFUL), equalTo(2));