### 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
CollectionUtil.timSort(executors); 
        TransportService serviceC = buildService("TS_C", CURRENT_VERSION, Settings.EMPTY);
        serviceC.registerRequestHandler("internal:action", ThreadPool.Names.SAME, TestRequest::new, (request, channel, task) -> {
            
        });
        CountDownLatch latch = new CountDownLatch(1);
        TransportResponseHandler<TransportResponse> transportResponseHandler = new TransportResponseHandler<TransportResponse>() {
            @Override
            public TransportResponse read(StreamInput in) {
                return TransportResponse.Empty.INSTANCE;
            }
            @Override
            public void handleResponse(TransportResponse response) {
                try {
                    fail("no response expected");
                } finally {
                    latch.countDown();
                }
            }
            @Override
            public void handleException(TransportException exp) {
                try {
                    if (exp instanceof SendRequestTransportException) {
                        assertTrue(exp.getCause().getClass().toString(), exp.getCause() instanceof NodeNotConnectedException);
                    } else {
                        
                        assertTrue(exp.getClass().toString(), exp instanceof NodeDisconnectedException);
                    }
                } finally {
                    latch.countDown();