ISSUE-4824: Regex patten based topic consumers prevent topic deletion

[sijie]

Original Issue: apache#4824

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Describe the bug
I am using Java client libraries. I created a consumer using topicsPattern for a regex pattern. As new topics matching the pattern get created, the consumer starts consuming from it. This is expected. However, I delete a topic that the consumer is consuming (even with an -f option); the topic does not get deleted (looks like it gets re-created). This is NOT EXPECTED, and is a DEFECT.

To Reproduce
Steps to reproduce the behavior:

1. Create a consumer using topicsPattern for a regex pattern say persistent://public/default/test.*
2. Create producers to start sending messages to topics test01, test02, test03 etc.
3. Once the consumer consumes the messages, stop producing to these topics
4. Execute ./pulsar-admin topics list public/default and verify that these topics do exist.
5. Execute ./pulsar-admin topics delete -f persistent://public/default/test02 to delete the topic.
6. No errors are shown.
7. However, execute ./pulsar-admin topics list public/default again and notice that test02 continues to exist.

Expected behavior
The system should allow deletion of topics even if regex pattern-based consumers have been attached to a topic.

Screenshots
NA

Desktop (please complete the following information):

• Java

Additional context
This problem gains importance as we want some listeners to ALL topics matching a certain pattern. And we have strong business reasons for the topics to be ephemeral in nature (create on demand, and delete when the work for that named topic is over)