### 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
private final TransportService service;
            TestRequestHandler(TransportService service) {
                this.service = service;
            }
            @Override
            public void messageReceived(TestRequest request, TransportChannel channel, Task task) throws Exception {
                if (randomBoolean()) {
                    Thread.sleep(randomIntBetween(10, 50));
                }
                if (fail.get()) {
                    throw new IOException("forced failure");
                }
                if (randomBoolean() && request.resendCount++ < 20) {
                    DiscoveryNode node = randomFrom(nodeA, nodeB, nodeC);
                    logger.debug("send secondary request from {} to {} - {}", toNodeMap.get(service), node, request.info);
                    service.sendRequest(
                        node,
                        "internal:action1",
                        new TestRequest("secondary " + request.info),
                        TransportRequestOptions.EMPTY,
                        new TransportResponseHandler<TestResponse>() {
                            private final String executor = randomBoolean() ? ThreadPool.Names.SAME : ThreadPool.Names.GENERIC;
                            @Override
                            public TestResponse read(StreamInput in) throws IOException {
                                return new TestResponse(in);
                            }
                            @Override