### 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 onConnectionOpened(final Transport.Connection connection) {
                    closeConnectionChannel(connection);
                    try {
                        assertBusy(() -> assertTrue(connection.isClosed()));
                    } catch (Exception e) {
                        throw new AssertionError(e);
                    }
                }
                @Override
                public void onConnectionClosed(Transport.Connection connection) {
                    connectionClosedListenerCalled.set(true);
                }
            });
            final ConnectionProfile.Builder builder = new ConnectionProfile.Builder();
            builder.addConnections(
                1,
                TransportRequestOptions.Type.BULK,
                TransportRequestOptions.Type.PING,
                TransportRequestOptions.Type.RECOVERY,
                TransportRequestOptions.Type.REG,
                TransportRequestOptions.Type.STATE
            );
            final ConnectTransportException e = expectThrows(
                ConnectTransportException.class,
                () -> openConnection(service, nodeA, builder.build())
            );
            assertThat(e, hasToString(containsString(("a channel closed while connecting"))));
            assertTrue(connectionClosedListenerCalled.get());
        }
    }