Support upgrading Ratify from single instance to HA

[FeynmanZhou]

What would you like to be added?

The default Ratify installation relies on a single Ratify pod processing all requests. For higher performance and availability requirements, Ratify can be set to run with multiple replicas and a shared state store as implanted in #901 . It requires users to install Ratify with HA mode from scratch.

As a user, I want to upgrade from a single Ratify instance (Pod) to HA mode for production deployment. This is a common scenario that users may want to switch to production after investigation and testing. Providing a flag such as --upgrade-ha to the installation command helm install ratify might be helpful.

Anything else you would like to add?

No response

Are you willing to submit PRs to contribute to this feature?

• [ ] Yes, I am willing to implement it.