Use grpc-interfaces crate in inspect-server

[gligneul]

📚 Context

The inspect-server builds the gRPC interface from scratch instead of re-using the shared crate that does the same thing.

✔️ Solution

Remove the code that builds the server-manager gRPC interface and use the crate grpc-interfaces.

[gligneul]

I will close this issue because the inspect API will stop using gRPC soon.