[Issue 1297][consumer] Fix DLQ producer name conflicts when there are same name consumers

[geniusjoe]

Fixes #1297
Master Issue: apache/pulsar#21589

Motivation

When multiple consumers with same name are using dlq policies at the same time, prompt will throw below exceptions:
ERRO[0069] Failed to create DLQ producer dlq-topic="persistent://<tenant>/<namespace>/<topic>-<subscription>-DLQ" error="server error: ProducerBusy: org.apache.pulsar.broker.service.BrokerServiceException$NamingException: Producer with name '-<subscription>-<consumerName>-DLQ' is already connected to topic"

Modifications

Add a random suffix in dlq producer name like: opt.Name = fmt.Sprintf("%s-%s-%s-%s-DLQ", r.topicName, r.subscriptionName, r.consumerName, generateRandomName())

Verifying this change

• Make sure that the change passes the CI checks.
  This change is already covered by existing tests, such as pulsar/consumer_test.go#TestDLQ(t *testing.T)

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (no)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)
  I will create a followup issue for adding the documentation later.