Netstack (#1403)

Add netstack support for the agent to run it without privileges.

- use interface for tun device
- use common IPC for userspace WireGuard integration
- move udpmux creation and sharedsock to tun layer

iface/tun.go

@@ -1,12 +1,18 @@
+//go:build !android
+// +build !android
+
 package iface
 
-type MobileIFaceArguments struct {
-	Routes        []string
-	Dns           string
-	SearchDomains []string
-}
+import (
+	"github.com/netbirdio/netbird/iface/bind"
+)
 
-// NetInterface represents a generic network tunnel interface
-type NetInterface interface {
+type wgTunDevice interface {
+	Create() (wgConfigurer, error)
+	Up() (*bind.UniversalUDPMuxDefault, error)
+	UpdateAddr(address WGAddress) error
+	WgAddress() WGAddress
+	DeviceName() string
 	Close() error
+	Wrapper() *DeviceWrapper // todo eliminate this function
 }