Allow use of GSM for superuser password secret

[sivaalamp]

This is similar to #458 except we read from GSM for the superuser password secret. We use the same feature flag as before. Here is a sample CR to enable it.

kind: VerticaDB
metadata:
  name: v
  annotations:
    vertica.com/use-gcp-secret-manager: "true" 
spec:
  superuserPasswordSecret: <full name of the secret in GSM>
...

The name of the GSM secret is taken from the existing spec.superuserPasswordSecret field.

Note, if GSM is being used we can't use the canary query for health probes as that depends on the superuser password being a k8s secret. Instead, we check if vertica is running by seeing if anyone is listening on the vertica client port.

[spilchen]

@sivaalamp thanks for your contribution. I don't normally do this, but since we are short on time I opted to apply the code review comments myself. This will shorten the review cycle and allow us to get it in QA hands sooner.