GRPC starts gRPC server on addr, logged as service.

HandleMetrics adds reg's prometheus handler on /metrics at mux.

HTTP starts HTTP server on addr using handler logged as service.

Metrics starts HTTP server on addr path /metrics using reg as prometheus handler.

RPC starts HTTP server on addr path /rpc using rcvr as JSON-RPC 2.0 handler.

RPCName starts HTTP server on addr path /rpc using rcvr as JSON-RPC 2.0 handler but uses the provided name for the type instead of the receiver's concrete type.

Ctx is a synonym for convenience.