Refactor `AbstractSimpleTransportTestCase` and `MockTransportService` to not use `Version.transportVersion` 
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
final String info;
        TestResponse(StreamInput in) throws IOException {
            super(in);
            this.info = in.readOptionalString();
        }
        TestResponse(String info) {
            this.info = info;
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            out.writeOptionalString(info);
        }
        @Override
        public String toString() {
            return "TestResponse{" + "info='" + info + '\'' + '}';
        }
    }
    public void testSendRandomRequests() throws InterruptedException {