Expose access to grpc.ServiceClient so we can create default golang client and get access to underlying GRPC client

[wolfy-j]

Is your feature request related to a problem? Please describe. For the PHP SDK, we have to generate proper client code.

Describe the solution you'd like Expose access to grpc.ServiceClient so we can create default golang client and get access to underlying GRPC client.

Additional context Add any other context or screenshots about the feature request here.