### 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 testTransportStatsWithException() throws Exception {
        MockTransportService serviceC = buildService("TS_C", version0, Settings.EMPTY);
        CountDownLatch receivedLatch = new CountDownLatch(1);
        CountDownLatch sendResponseLatch = new CountDownLatch(1);
        Exception ex = new RuntimeException("boom");
        ex.setStackTrace(new StackTraceElement[0]);
        serviceB.registerRequestHandler("internal:action", ThreadPool.Names.SAME, TestRequest::new, (request, channel, task) -> {
            
            threadPool.generic().execute(new AbstractRunnable() {
                @Override
                public void onFailure(Exception e) {
                    try {
                        channel.sendResponse(e);
                    } catch (IOException e1) {
                        throw new UncheckedIOException(e1);
                    }
                }
                @Override
                protected void doRun() throws Exception {
                    receivedLatch.countDown();
                    sendResponseLatch.await();
                    onFailure(ex);
                }
            });
        });
        CountDownLatch responseLatch = new CountDownLatch(1);
        AtomicReference<TransportException> receivedException = new AtomicReference<>(null);
        TransportResponseHandler<TransportResponse.Empty> transportResponseHandler = new TransportResponseHandler.Empty() {