The server component of linera-rpc has a circular (runtime) dependency on linera-service

[Twey]

The server and client in linera-rpc are not in fact dual: while the ‘server’ refers to a validator shard server, the ‘client’ is in fact a client for the gRPC proxy service written in linera-service/src/grpc_proxy.rs. This prohibits testing linera-rpc against itself, since it must have a linera-proxy running — a binary from linera-service, which it therefore can't start for testing without a circular dependency on linera-service.