[LI-HOTFIX] Add federated topic znode delete rpc

[kehuum]

This PR adds

1. delete federated topic rpc that deletes the znode entry under /federatedTopics/topicName (value = namespace name)
2. zk function to get all federated topics as a set of string, in the format of /namespaceName/topicName for easier usage and avoid duplicate code in kafka-server

LI_DESCRIPTION =
In order to make kafka broker understand new acl, it will need to understand the topic name and its corresponding namespace. So when a new kafka topic is deleted by xmd-service, the corresponding znode will also be deleted in the above new znode directory.

Added integ-test to verify create and delete logic

EXIT_CRITERIA = We can deprecate this pr when all kafka clients have been migrated to xinfra clients and all topic CUDs go through xmd, then we don't need kafka broker to understand both old and new topic acl, it will only need to understand the new acl.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)