Fix retry policy not effective with partitioned topic

[wuYin]

Issue

Retry policy not effective with partitioned topic.

• reproduction
  topic-01 have 2 partitions:

   client, _ := pulsar.NewClient(pulsar.ClientOptions{URL: "pulsar://localhost:6650"})
   consumer, _ := client.Subscribe(pulsar.ConsumerOptions{
   	Topic:            "topic-01",
   	SubscriptionName: "my-sub",
   	RetryEnable:      true,
   	DLQ:              &pulsar.DLQPolicy{MaxDeliveries: 2},
   })
   msg, _ := consumer.Receive(context.Background())
   consumer.ReconsumeLater(msg, 5*time.Second)

• logs

  WARN[0000] consumer of topic [persistent://public/default/topic-01-partition-0] not exist unexpectedly  topic=" [persistent://public/default/topic-01 persistent://platform/psr/my-sub-RETRY]"
  

Cause

For MultiTopicConsumer consumers map filed:

• key: FQDN topics, without partition number suffix.
• value: consumer instance.

ReconsumeLater using msg's partition number suffix topic as key, to find consumer in consumers, but allways not found, lead to Retry policy not effective.

Modifications

• Trim partition number in partitioned topic before using it

Verifying this change

• Make sure that the change passes the CI checks.