TUN inbound: Add gateway, dns, autoSystemRoutingTable, autoOutboundsInterface for Windows (#5887)

And refactor `mtu` to support setting IPv4/v6 separately

Example: https://github.com/XTLS/Xray-core/pull/5887#issue-4198837696

proxy/tun/stack_gvisor.go

@@ -34,23 +34,18 @@ const (
 // stackGVisor is ip stack implemented by gVisor package
 type stackGVisor struct {
 	ctx         context.Context
-	tun         GVisorTun
+	tun         Tun
 	idleTimeout time.Duration
 	handler     *Handler
 	stack       *stack.Stack
 	endpoint    stack.LinkEndpoint
 }
 
-// GVisorTun implements a bridge to connect gVisor ip stack to tun interface
-type GVisorTun interface {
-	newEndpoint() (stack.LinkEndpoint, error)
-}
-
 // NewStack builds new ip stack (using gVisor)
 func NewStack(ctx context.Context, options StackOptions, handler *Handler) (Stack, error) {
 	gStack := &stackGVisor{
 		ctx:         ctx,
-		tun:         options.Tun.(GVisorTun),
+		tun:         options.Tun,
 		idleTimeout: options.IdleTimeout,
 		handler:     handler,
 	}