### 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`)
server/src/main/java/org/elasticsearch/transport/TransportService.java
public ConnectionManager getConnectionManager() {
        return connectionManager;
    }
    public RecyclerBytesStreamOutput newNetworkBytesStream() {
        return transport.newNetworkBytesStream();
    }
    static class HandshakeRequest extends TransportRequest {
        public static final HandshakeRequest INSTANCE = new HandshakeRequest();
        HandshakeRequest(StreamInput in) throws IOException {
            super(in);
        }
        private HandshakeRequest() {}
    }
    public static class HandshakeResponse extends TransportResponse {
        private final Version version;
        @Nullable 
        private final String buildHash;
        private final DiscoveryNode discoveryNode;
        private final ClusterName clusterName;
        public HandshakeResponse(Version version, String buildHash, DiscoveryNode discoveryNode, ClusterName clusterName) {
            this.buildHash = Objects.requireNonNull(buildHash);
            this.discoveryNode = Objects.requireNonNull(discoveryNode);
            this.version = Objects.requireNonNull(version);
            this.clusterName = Objects.requireNonNull(clusterName);
        }
        public HandshakeResponse(StreamInput in) throws IOException {
            super(in);
            
            
            version = Version.readVersion(in);