broker: refactor (#396)

* remove subscribe from server
* remove publish from client
* broker package refactoring

Co-authored-by: vtolstov <vtolstov@users.noreply.github.com>
Reviewed-on: #396
Co-authored-by: Vasiliy Tolstov <v.tolstov@unistack.org>
Co-committed-by: Vasiliy Tolstov <v.tolstov@unistack.org>

errors/errors.proto

@@ -17,7 +17,7 @@ syntax = "proto3";
 package micro.errors;
 
 option cc_enable_arenas = true;
-option go_package = "go.unistack.org/micro/v3/errors;errors";
+option go_package = "go.unistack.org/micro/v4/errors;errors";
 option java_multiple_files = true;
 option java_outer_classname = "MicroErrors";
 option java_package = "micro.errors";