Confluent kafka downgrade + worker reregistration deduplication

[Theodlz]

This PR:

• downgrades the "dependabot updated" confluent-kafka (from 2.6.0 back to 2.5.3), as the new version creates authentication issues.
• Registering/restarting new topic listener now also avoids registering workers if they are already registered on the cluster/scheduler, which created memory leaks when we kept timing out from the kafka topics and registering the workers again and again.
• I also remove some unnecessary logs from the ZTF workers, that have been polluting the logs for some time now and make it hard to find relevant lines when this kind of error occurs.

[Theodlz]

self merging as this is preventing us from running Kowalski in production!

[Theodlz]

will merge once green