Migrate KatibCertGenerator to OPA CertController

[tenzen-y]

/kind feature

Describe the solution you'd like
[A clear and concise description of what you want to happen.]
Today, we maintain the katib-cert-generator to generate certifications for the webhook.
But, it doesn't have some useful features like a certification rotation mechanism.

So, we should migrate the katib-cert-generator to open-policy-agent/cert-controller.

This training-operator cert generation mechanism would be a good example to introduce the opa/cert-controller to the katib: https://github.com/kubeflow/training-operator/blob/e85dbf9e010421813ea03bf0f82a4801f4587989/pkg/cert/cert.go

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

---

Love this feature? Give it a 👍 We prioritize the features with the most 👍