It will be troublesome not to allow just identifying gRPC target host name as grpcCall argument. Specifically, we should provide fallback mechanism if GrpcService parse failed from bytes stream.

We will get into some trouble without this feature when we introduce support gRPC client from proxy-wasm SDK such as Rust. (It doesn't have gRPC client support right now), because it will be required new code for the desired language generated from Envoy API proto.

My expected behavior is when we failed to parse bytes stream, then try to parse the bytes stream as hostname. We will get ParseFailure after failed to parse hostname.