### 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
final int value1;
        Version0Response(int value1) {
            this.value1 = value1;
        }
        Version0Response(StreamInput in) throws IOException {
            this.value1 = in.readInt();
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            out.writeInt(value1);
        }
    }
    static class Version1Response extends Version0Response {
        final int value2;
        Version1Response(int value1, int value2) {
            super(value1);
            this.value2 = value2;
        }
        Version1Response(StreamInput in) throws IOException {
            super(in);
            if (in.getVersion().onOrAfter(version1)) {
                value2 = in.readInt();
            } else {
                value2 = 0;
            }
        }
        @Override