Summary: save temporary root CA with a unique label field to avoid constraint check failure when rotating root CA for multiple universes with the same old root CA

Test Plan: create two universes with the same root CA and initiate root CA rotation simultaneously

Reviewers: vbansal, nsingh

Reviewed By: vbansal

Subscribers: yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D45764