### 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
holder.action(),
                                "request_id [" + requestId + "] timed out after [" + (timeoutTime - sentTime) + "ms]"
                            )
                        );
                } else {
                    
                    timeoutInfoHandlers.remove(requestId);
                }
            }
        }
        /**
         * cancels timeout handling. this is a best effort only to avoid running it. remove the requestId from {@link #responseHandlers}
         * to make sure this doesn't run.
         */
        public void cancel() {
            assert responseHandlers.contains(requestId) == false
                : "cancel must be called after the requestId [" + requestId + "] has been removed from clientHandlers";
            if (cancellable != null) {
                cancellable.cancel();
            }
        }
        @Override
        public String toString() {
            return "timeout handler for [" + requestId + "][" + action + "]";
        }
        private void scheduleTimeout(TimeValue timeout) {
            this.cancellable = threadPool.schedule(this, timeout, ThreadPool.Names.GENERIC);
        }
    }
    static class TimeoutInfoHolder {