ISSUE-6257: Broker Interceptors

[sijie]

Original Issue: apache#6257

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Is your feature request related to a problem? Please describe.
Currently, when a client connects to the broker, a new subscribe created only prints logs into the broker log. This is not convenient for doing some audit work at the broker side. So it's better to introduce a new mechanism for easy access to these data.

And we have introduced the namespace change event https://github.com/apache/pulsar/wiki/PIP-39%3A-Namespace-Change-Events. The implementation introduce Pulsar system topic. We can use the same approach to achieve this feature.