CLOUDP-235689: CI fixes for unify multi-cluster replica sets feature branch

[m1kola]

Summary

• Removed the unused getReplicaSetMultiClusterMap function to make the linter happy
• Reverted GetMultiServiceFQDN back to it's original version as it was breaking a lot of unit and e2e tests.

Proof of Work

CI must be greener. Still need to address more issues.

Checklist

• Have you linked a jira ticket and/or is the ticket in the title?
• Have you checked whether your jira ticket required DOCSP changes?
• Have you added changelog file?
  • use skip-changelog label if not needed
  • refer to Changelog files and Release Notes section in CONTRIBUTING.md for more details