### 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 
x-pack/plugin/async-search/src/internalClusterTest/java/org/elasticsearch/xpack/search/CrossClusterAsyncSearchIT.java
}
    }
    public void testRemoteClusterOnlyCCSWithFailuresOnAllShards() throws Exception {
        
        
        SearchListenerPlugin.negate();
        Map<String, Object> testClusterInfo = setupTwoClusters();
        String remoteIndex = (String) testClusterInfo.get("remote.index");
        int remoteNumShards = (Integer) testClusterInfo.get("remote.num_shards");
        boolean skipUnavailable = (Boolean) testClusterInfo.get("remote.skip_unavailable");
        SubmitAsyncSearchRequest request = new SubmitAsyncSearchRequest(REMOTE_CLUSTER + ":" + remoteIndex);
        request.setCcsMinimizeRoundtrips(randomBoolean());
        request.setWaitForCompletionTimeout(TimeValue.timeValueMillis(1));
        request.setKeepOnCompletion(true);
        if (randomBoolean()) {
            request.setBatchedReduceSize(randomIntBetween(2, 256));
        }
        boolean dfs = randomBoolean();
        if (dfs) {
            request.getSearchRequest().searchType(SearchType.DFS_QUERY_THEN_FETCH);
        }
        
        ThrowingQueryBuilder queryBuilder = new ThrowingQueryBuilder(randomLong(), new IllegalStateException("index corrupted"), -1);
        request.getSearchRequest().source(new SearchSourceBuilder().query(queryBuilder).size(10));
        boolean minimizeRoundtrips = TransportSearchAction.shouldMinimizeRoundtrips(request.getSearchRequest());
        AsyncSearchResponse response = submitAsyncSearch(request);
        assertNotNull(response.getSearchResponse());
        waitForSearchTasksToFinish();
        {
            AsyncSearchResponse finishedResponse = getAsyncSearch(response.getId());