### 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/transport/TransportService.java
listener.onResponseSent(requestId, action, error);
            }
        }
        @Override
        public void onRequestSent(
            DiscoveryNode node,
            long requestId,
            String action,
            TransportRequest request,
            TransportRequestOptions finalOptions
        ) {
            for (TransportMessageListener listener : listeners) {
                listener.onRequestSent(node, requestId, action, request, finalOptions);
            }
        }
        @Override
        @SuppressWarnings("rawtypes")
        public void onResponseReceived(long requestId, Transport.ResponseContext holder) {
            for (TransportMessageListener listener : listeners) {
                listener.onResponseReceived(requestId, holder);
            }
        }
    }
    private static class PendingDirectHandlers extends AbstractRefCounted {