chore: add GSO support for TUN

lwip had been dropped, also cgo build will be removed

constant/tun.go

@@ -9,14 +9,12 @@ import (
 var StackTypeMapping = map[string]TUNStack{
 	strings.ToLower(TunGvisor.String()): TunGvisor,
 	strings.ToLower(TunSystem.String()): TunSystem,
-	strings.ToLower(TunLWIP.String()):   TunLWIP,
 	strings.ToLower(TunMixed.String()):  TunMixed,
 }
 
 const (
 	TunGvisor TUNStack = iota
 	TunSystem
-	TunLWIP
 	TunMixed
 )
 
@@ -64,8 +62,6 @@ func (e TUNStack) String() string {
 		return "gVisor"
 	case TunSystem:
 		return "System"
-	case TunLWIP:
-		return "LWIP"
 	case TunMixed:
 		return "Mixed"
 	default: