GCP Secret Manager Type can't get secret key If GCP Secret Manager use JSON

[kingbj940429]

Is your feature request related to a problem? Please describe.
If use GCP Secret Manager, It can't parse json data

example,
I have a GCP Secret Manager named kingbj0429-secret
and kingbj0429-secret has various secrets as json

{
  db-username: admin
  db-password: admin
}

like this situatiom, argo-vault-plugin for GCP Secret Manager can't parse db-password secret

argo-vault-plugin for GCP Secret Manager get all json data itself.

so I can't use secret with GCP

apiVersion: v1
data:
  #-- <path:projects/kingbj0429-447407/secrets/kingbj0429-secret#db-password>
  test: PHBhdGg6cHJvamVjdHMva2luZ2JqMDQyOS00NDc0MDcvc2VjcmV0cy9raW5nYmowNDI5LXNlY3JldCNkYi1wYXNzd29yZD4=
kind: Secret
metadata:
  name: test-secrets
  namespace: arc-system
type: Opaque

Describe the solution you'd like

this is gcpsecretmanager.go's code

It can only use secret manager name as key
json's key can't be key

so I want to add function for parsing json key like awssecretmanager.go's GetSecrets Function

Describe alternatives you've considered
maybe a implement is needed

Additional context
Can I Pull Request this?

I'll code about this