Evaluate Container Networking Interface with Quilkin

[XAMPPRocky]

Last month the "Container Networking Interface" was stabilised. CNI plugins allow for cloud vendor agnostic networking between nodes, and provides plugin functionality, allowing applications to extend networking behaviour. We should look into and evaluate having a CNI plugin for Quilkin, what features it should have, and how it should behave. This has the potential to cover a lot of the network optimisations and integrations. For example, integrating with the Firewall CNI plugin, would allow Quilkin to integrate with both firewalld and iptables, as they're both compatible CNI firewall backends.