Add gRPC intercept loggers

We now have Praefect running in our staging environment, but it isn't generating enough logging on requests to help ops understand how well it is operating. This change introduces a unary and streaming gRPC intercept logger. These are the same set of loggers currently used on Gitaly: https://gitlab.com/gitlab-org/gitaly/blob/b69f0b8837eca8ebe716ef03338292a185b0ce65/internal/server/server.go#L84-100