Add timing diagrams and flowcharts to each core process.

[kuangye098]

1. Client

   • 连接池管理（连接、重连接）
   • PARTITIONED_METADATA_RESPONSE
   • LOOKUP_RESPONSE
   • GET_SCHEMA_RESPONSE

2. Producer

   • 连接、重连接
   • (批量)发送消息
   • 关闭生产者
   • GET_TOPICS_OF_NAMESPACE_RESPONSE

3. Consumer

   • 连接、重连接
   • SUBSCRIBE
   • FLOW
   • MESSAGE
   • REDELIVER_UNACKNOWLEDGED_MESSAGES
   • 消息消费
   • 消息重试与死信消息
   • ACTIVE_CONSUMER_CHANGE
   • 关闭消费者

4. Broker

   • PARTITIONED_METADATA
   • LOOKUP
   • GET_SCHEMA
   • CONNECT
   • PRODUCER
   • SEND
   • CLOSE_PRODUCER
   • SUBSCRIBE
   • FLOW
   • MESSAGE
   • REDELIVER_UNACKNOWLEDGED_MESSAGES
   • ACK
   • SEEK
   • ACTIVE_CONSUMER_CHANGE
   • UNSUBSCRIBE
   • CLOSE_CONSUMER
   • REACHED_END_OF_TOPIC
   • CONSUMER_STATS
   • GET_LAST_MESSAGE_ID
   • GET_TOPICS_OF_NAMESPACE