support default Dynamic IPv6 subnet allocation and ip6tables

[finch71]

What is the problem you're trying to solve

nerdctl doesn't listen on ipv6 by default

Describe the solution you'd like

https://docs.docker.com/engine/daemon/ipv6/

Additional context

#127

[finch71]

At the moment it requires user to configure every network one by one. and it doesn't support configuring ip6tables

cat >/etc/cni/net.d/10-mynet.conf
{
        "cniVersion": "0.2.0",
        "name": "mynet",
        "type": "bridge",
        "bridge": "cni0", 
        "ipam": {
                "type": "host-local",
                "subnet": "2001:db8::/96",
                "routes": [
                        { "dst": "::/0" },
                        { "dst": "2001:db8::/96" }
                ]
        }
}


./nerdctl --snapshotter native run --network mynet  -d -p 80:80  alpine  sleep 300

./nerdctl ps
CONTAINER ID    IMAGE                              COMMAND        CREATED               STATUS    PORTS                                NAMES
7e31884d8ba0    docker.io/library/alpine:latest    "sleep 300"    About a minute ago    Up        0.0.0.0:80->80/tcp, :::80->80/tcp