Incorporate new ns_server endpoints for collections

With MB-42712, the endpoints to retrieve collection manifest, create/delete scopes and collections are going to change. These changes have to be incorporated on GSI stack.

Specifically, the pools.Refresh() method has to be updated to not query the "/collections" endpoint. Also, the test framework has to be updated to incorporate the new endpoints for creation and deletion of scopes/collections

This MB is filed for tracking purpose on GSI side.