Remove legacy code (#3838)

* Add feature migration notice

* Remove legacy code of transport processing

* Clear legacy proto field

* Fix missing

* Unify protocolname

* Test remove

* Supressor

* Weird code

* Remove errorgen related comments

transport/internet/grpc/config.go

@@ -8,8 +8,6 @@ import (
 	"github.com/xtls/xray-core/transport/internet"
 )
 
-const protocolName = "grpc"
-
 func init() {
 	common.Must(internet.RegisterProtocolConfigCreator(protocolName, func() interface{} {
 		return new(Config)