RocketMQ 5.0 POP消费模式

1）RebalanceService#run:重平衡线程
2）MQClientInstance#doRebalance
3）MQConsumerInner#doRebalance
4）DefaultMQPushConsumerImpl#doRebalance

说明：如果配置了pop模式，将会走if分支

5)RebalanceImpl#dispatchPopPullRequest
6)RebalancePushImpl#dispatchPopPullRequest
7)PullMessageService#run

8)DefaultMQPushConsumerImpl#popMessage
9)ConsumeMessagePopConcurrentlyService#submitPopConsumeRequest
说明：提交任务到线程池，ConsumeMessagePopConcurrentlyService.ConsumeRequest

Broker处理POP消费模式的两个处理器
PopMessageProcessor
AckMessageProcessor