CMEK support for secrets-sync with GCP secret manager

[t-indumathy]

Is your feature request related to a problem? Please describe. There is a gap in the current secret sync approach from vault to GCP secret manager, where we cannot pass any CMEK for encryption.

Describe the solution you'd like A field in the CLI/API to accept the CMEK while syncing the secrets from vault to gcp-sm is required.

Describe alternatives you've considered No alternatives. Left with secret sprawl. We cannot use this feature due to this gap.