### 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
Version0Response version0Response = submitRequest(
            serviceA,
            nodeA,
            "internal:version",
            version0Request,
            new TransportResponseHandler<Version0Response>() {
                @Override
                public Version0Response read(StreamInput in) throws IOException {
                    return new Version0Response(in);
                }
                @Override
                public void handleResponse(Version0Response response) {
                    assertThat(response.value1, equalTo(1));
                }
                @Override
                public void handleException(TransportException exp) {
                    logger.error("Unexpected failure", exp);
                    fail("got exception instead of a response: " + exp.getMessage());
                }
            }
        ).get();
        assertThat(version0Response.value1, equalTo(1));
    }
    public void testMockFailToSendNoConnectRule() throws Exception {
        serviceA.registerRequestHandler(
            "internal:sayHello",
            ThreadPool.Names.GENERIC,
            StringMessageRequest::new,
            (request, channel, task) -> {
                assertThat("moshe", equalTo(request.message));