Add google cloud logging destination handler for consolidated audit event destinations

As part of &12339, we need to add validation to config property for audit event streaming destinations of category gcp in https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/models/concerns/audit_events/externally_streamable.rb.

References:

1. Validations are already present in https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/models/concerns/audit_events/gcp_externally_destinationable.rb.
2. MR for handling custom http validations !143914 (merged) can also be considered as a reference.