net/portmapper: add upnp port mapping

Add in UPnP portmapping, using goupnp library in order to get the UPnP client and run the
portmapping functions. This rips out anywhere where UPnP used to be in portmapping, and has a
flow separate from PMP and PCP.

RELNOTE=portmapper now supports UPnP mappings

Fixes #682
Updates #2109

Signed-off-by: julianknodt <julianknodt@gmail.com>

tstest/integration/testcontrol/testcontrol.go

@@ -636,6 +636,9 @@ func (s *Server) MapResponse(req *tailcfg.MapRequest) (res *tailcfg.MapResponse,
 		Domain:          string(user.Domain),
 		CollectServices: "true",
 		PacketFilter:    tailcfg.FilterAllowAll,
+		Debug: &tailcfg.Debug{
+			DisableUPnP: "true",
+		},
 	}
 	for _, p := range s.AllNodes() {
 		if p.StableID != node.StableID {