[Polish] Move example code to somewhere?

[GOODBOY008]

[lizhimins]

The concept of SimpleConsumer is introduced in RocketMQ 5.0. The demo here is a 4. x consumer demonstration, which can be distinguished by renaming.

在 RocketMQ 5.0 中引入了 SimpleConsumer 的概念，这里是 4.x 版本的消费者演示，可以通过重命名来区分下。