Google Cloud KMS provider

This protection scheme uses Google Cloud Key Management Service (https://cloud.google.com/security-key-management) for encryption and decryption. Google Cloud KMS configuration properties are to be stored in the bootstrap-gcp.conf file, as referenced in the bootstrap.conf of NiFi or NiFi Registry. Credentials must be configured as per the following documentation: https://cloud.google.com/kms/docs/reference/libraries