Refactor `AbstractSimpleTransportTestCase` and `MockTransportService` to not use `Version.transportVersion` 
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
out.writeLong(timeout);
        }
    }
    static class StringMessageResponse extends TransportResponse {
        private final String message;
        StringMessageResponse(String message) {
            this.message = message;
        }
        StringMessageResponse(StreamInput in) throws IOException {
            this.message = in.readString();
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            out.writeString(message);
        }
    }
    public static class Version0Request extends TransportRequest {
        int value1;
        Version0Request() {}
        Version0Request(StreamInput in) throws IOException {
            super(in);
            value1 = in.readInt();
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            super.writeTo(out);
            out.writeInt(value1);
        }
    }
    public static class Version1Request extends Version0Request {