Use "Get" by secret resourcename than "Watch" on all secrets.

[eatwithforks]

https://github.com/open-policy-agent/cert-controller/blob/master/pkg/rotator/rotator.go#L587-L593

would be less overhead to do a GET on secret by secret-name than watching the full list of secrets

[mozillazg]

+1 for avoid watch and list all secrets.