### 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`)
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
public void handleResponse(TestResponse response) {
                                try {
                                    if (randomBoolean()) {
                                        Thread.sleep(randomIntBetween(10, 50));
                                    }
                                    logger.debug("send secondary response {}", response.info);
                                    channel.sendResponse(response);
                                } catch (Exception e) {
                                    throw new RuntimeException(e);
                                }
                            }
                            @Override
                            public void handleException(TransportException exp) {
                                try {
                                    logger.debug("send secondary exception response for request {}", request.info);
                                    channel.sendResponse(exp);
                                } catch (Exception e) {
                                    throw new RuntimeException(e);
                                }
                            }
                            @Override
                            public String executor() {
                                return executor;
                            }
                        }
                    );
                } else {
                    logger.debug("send response for {}", request.info);
                    channel.sendResponse(new TestResponse("Response for: " + request.info));
                }