[improve][test] Do Not Merge: Debug logs added to PulsarWorkerRebalanceDrainTest to investigate flakiness

[ShivrajJ]

Main Issue: #xyz

Motivation

The integration test PulsarWorkerRebalanceDrainTest#testRebalanceWorkers is exhibiting flaky behaviour. It fails sometimes when the function worker leader unexpectedly changes when adding more workers as part of the test. These changes are made to add more debug-level logs in order to investigate the cause of this behaviour.

Modifications

• Added a function to retrieve topic stats from the proxy container for the coordination topic.
• Added log statements to report the topic stats before and after adding new function workers.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

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

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete