Support implicit credentials (f.e. Workload Identity in k8s) for GCP Secrets Manager client creation like it does for pubsub client:

this function
https://github.com/dapr/components-contrib/blob/master/secretstores/gcp/secretmanager/secretmanager.go#L66

should be similar to this one
https://github.com/dapr/components-contrib/blob/master/pubsub/gcp/pubsub/pubsub.go#L152