feat(netlink): detect IPv6 using query to address

- If a default IPv6 route is found, query the ip:port defined by `IPV6_CHECK_ADDRESS` to check for internet access

internal/netlink/mocks_generate_test.go

@@ -0,0 +1,3 @@
+package netlink
+
+//go:generate mockgen -destination=mocks_test.go -package=$GOPACKAGE . Firewall