### 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
channel.sendResponse(new StringMessageResponse("hello " + request.message));
                    } catch (IOException e) {
                        logger.error("Unexpected failure", e);
                        fail(e.getMessage());
                    }
                } finally {
                    inFlight.release();
                    if ("forever".equals(message)) {
                        doneWaitingForever.countDown();
                    }
                }
            }
        );
        final CountDownLatch latch = new CountDownLatch(1);
        Future<StringMessageResponse> res = submitRequest(
            serviceB,
            nodeA,
            "internal:sayHelloTimeoutDelayedResponse",
            new StringMessageRequest("forever"),
            TransportRequestOptions.timeout(HUNDRED_MS),
            new TransportResponseHandler<StringMessageResponse>() {
                @Override
                public StringMessageResponse read(StreamInput in) throws IOException {
                    return new StringMessageResponse(in);
                }
                @Override
                public String executor() {
                    return ThreadPool.Names.GENERIC;
                }
                @Override