### 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/test/java/org/elasticsearch/action/search/SearchResponseTests.java
},
                  "_clusters": {
                    "total": 4,
                    "successful": 1,
                    "skipped": 1,
                    "running":0,
                    "partial": 1,
                    "failed": 1,
                    "details": {
                      "(local)": {
                        "status": "successful",
                        "indices": "foo,bar*",
                        "took": 1000,
                        "timed_out": false,
                        "_shards": {
                          "total": 5,
                          "successful": 5,
                          "skipped": 1,
                          "failed": 0
                        }
                      },
                      "cluster_1": {
                        "status": "skipped",
                        "indices": "foo,bar*",
                        "took": 1000,
                        "timed_out": false,
                        "_shards": {
                          "total": 5,
                          "successful": 0,
                          "skipped": 0,