### Description

The `sendRequest` method is asynchronous and notifies a 
`TransportResponseHandler` when it completes the excecution
(successfully or unsuccessfully). 

When opening the connection we only catch `NodeNotConnectedException`
( https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/transport/TransportService.java#L719 ) which is currently fine as no implementations
throw other type of exception however, it'd be best to catch `Exception` here
so the `handler` gets notified of potential exceptions (as opposed to the caller
having to `try/catch` the call to `sendRequest`)
server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationDiagnosticsService.java
void cancelPollingRemoteMasterStabilityDiagnostic() {
        assert ThreadPool.assertCurrentThreadPool(ClusterApplierService.CLUSTER_UPDATE_THREAD_NAME);
        if (remoteCoordinationDiagnosisTask != null) {
            Scheduler.Cancellable task = remoteCoordinationDiagnosisTask.get();
            if (task != null) {
                task.cancel();
            }
            remoteCoordinationDiagnosisResult = null;
            remoteCoordinationDiagnosisTask = null;
        }
    }
    
    record ClusterFormationStateOrException(
        ClusterFormationFailureHelper.ClusterFormationState clusterFormationState,
        Exception exception
    ) {
        ClusterFormationStateOrException {
            if (clusterFormationState != null && exception != null) {
                throw new IllegalArgumentException("Cluster formation state and exception cannot both be non-null");
            }
        }
        ClusterFormationStateOrException(ClusterFormationFailureHelper.ClusterFormationState clusterFormationState) {
            this(clusterFormationState, null);
        }
        ClusterFormationStateOrException(Exception exception) {
            this(null, exception);
        }
    }
    public record CoordinationDiagnosticsResult(
        CoordinationDiagnosticsStatus status,