nixos/modules/networking/wg-quick Add wg-quick options support

This is an implementation of wireguard support using wg-quick config
generation.

This seems preferrable to the existing wireguard support because
it handles many more routing and resolvconf edge cases than the
current wireguard support.

It also includes work-arounds to make key files work.

This has one quirk:
We need to set reverse path checking in the firewall to false because
it interferes with the way wg-quick sets up its routing.