rpc: add unary+streaming interceptors to log all errors

Not all errors that occur when serving client requests in the gRPC
server are logged. As a result, at times, we can be lacking critic
information that can be used to debug issues that pop up. With this PR,
we create a basic streaming+unary interceptor that will log all errors
that occur when servicing calls.

The current format looks something like this in the logs when an error
occurs:

```
[ERR] RPCS: [/lnrpc.Lightning/SendCoins]: decoded address is of unknown format
```

rpcserver.go

@@ -560,6 +560,15 @@ func newRPCServer(s *server, macService *macaroons.Service,
 	unaryInterceptors := append(macUnaryInterceptors, promUnaryInterceptors...)
 	strmInterceptors := append(macStrmInterceptors, promStrmInterceptors...)
 
+	// We'll also add our logging interceptors as well, so we can
+	// automatically log all errors that happen during RPC calls.
+	unaryInterceptors = append(
+		unaryInterceptors, errorLogUnaryServerInterceptor(rpcsLog),
+	)
+	strmInterceptors = append(
+		strmInterceptors, errorLogStreamServerInterceptor(rpcsLog),
+	)
+
 	// If any interceptors have been set up, add them to the server options.
 	if len(unaryInterceptors) != 0 && len(strmInterceptors) != 0 {
 		chainedUnary := grpc_middleware.WithUnaryServerChain(