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/splithttp/splithttp.go

@@ -1,18 +1,3 @@
 package splithttp
 
-import (
-	"context"
-
-	"github.com/xtls/xray-core/common"
-	"github.com/xtls/xray-core/common/errors"
-)
-
-//go:generate go run github.com/xtls/xray-core/common/errors/errorgen
-
 const protocolName = "splithttp"
-
-func init() {
-	common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
-		return nil, errors.New("splithttp is a transport protocol.")
-	}))
-}