### 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
TransportStats transportStats = serviceC.transport.getStats(); 
                assertEquals(1, transportStats.getRxCount());
                assertEquals(2, transportStats.getTxCount());
                assertEquals(25, transportStats.getRxSize().getBytes());
                assertEquals(111, transportStats.getTxSize().getBytes());
            });
            sendResponseLatch.countDown();
            responseLatch.await();
            stats = serviceC.transport.getStats(); 
            assertEquals(2, stats.getRxCount());
            assertEquals(2, stats.getTxCount());
            assertEquals(50, stats.getRxSize().getBytes());
            assertEquals(111, stats.getTxSize().getBytes());
        } finally {
            serviceC.close();
        }
    }
    public void testAcceptedChannelCount() throws Exception {
        assertBusy(() -> {
            TransportStats transportStats = serviceA.transport.getStats();
            assertEquals(channelsPerNodeConnection(), transportStats.getServerOpen());
        });
        assertBusy(() -> {
            TransportStats transportStats = serviceB.transport.getStats();
            assertEquals(channelsPerNodeConnection(), transportStats.getServerOpen());
        });
        serviceA.close();
        assertBusy(() -> {
            TransportStats transportStats = serviceB.transport.getStats();
            assertEquals(0, transportStats.getServerOpen());