### 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
originalTransport.openConnection(node, connectionProfile, future);
            try (Transport.Connection connection = future.actionGet()) {
                assertBusy(() -> { assertTrue(originalTransport.getKeepAlive().successfulPingCount() > 30); });
                assertEquals(0, originalTransport.getKeepAlive().failedPingCount());
            }
        }
    }
    public void testTcpHandshake() {
        assumeTrue("only tcp transport has a handshake method", serviceA.getOriginalTransport() instanceof TcpTransport);
        ConnectionProfile connectionProfile = ConnectionProfile.buildDefaultConnectionProfile(Settings.EMPTY);
        try (TransportService service = buildService("TS_TPC", Version.CURRENT, Settings.EMPTY)) {
            DiscoveryNode node = new DiscoveryNode(
                "TS_TPC",
                "TS_TPC",
                service.boundAddress().publishAddress(),
                emptyMap(),
                emptySet(),
                version0
            );
            PlainActionFuture<Transport.Connection> future = PlainActionFuture.newFuture();
            serviceA.getOriginalTransport().openConnection(node, connectionProfile, future);
            try (Transport.Connection connection = future.actionGet()) {
                assertEquals(connection.getVersion(), Version.CURRENT);
            }
        }
    }
    public void testTcpHandshakeTimeout() throws IOException {
        try (ServerSocket socket = new MockServerSocket()) {
            socket.bind(getLocalEphemeral(), 1);
            socket.setReuseAddress(true);