support default Dynamic IPv6 subnet allocation and ip6tables

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

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    

[Zheaoli]

For now, the nerdctl has already support IPV6, I'm not sure what behavior is you want. Would you mind provide more detail about this?

In docker if I set
{ "ipv6": true, "ip6tables":true, "fixed-cidr-v6": "2001:db8:1::/64" }

ipv6 will enable IPv6 networking on all the default networks and it will automatically assign ip address without configure every .yml file

similarly, ip6tables adds additional IPv6 packet filter rules to iptables automatically (so that one can further configure rules for every pod)