Document ipv4/ipv6 dualstack settings

Bug Report

Description

Dualstack seems to work according to https://github.com/siderolabs/talos/issues/8115#issue-2056553134.
But I still couldn't find any documentation about this - apart from some github issues around the topic.
It feels clunky & definitely not like it's a supported configuration.
If you add ipv6 - even if it's just as dualstack setup - to your docs, it'd definitely be a statement that it's a supported feature and you have it in mind for future development.

Some ideas for the docs

• The kubernetes docs for dualstack describe several flags that need to be set. How do I set them on Talos?

Some cases you could include:

Dualstack for nodes & controlplane

This comes from reading the k8s & kubeadm dualstack docs and aims at specifying dualstack node-ips either statically or via DHCP/DHCPv6.

As an improvement example, why is there no machine.network.ipv6: true which also automatically enables DHCPv6?
From what I read, I need to go via machine.network.interfaces[...].dhcpOptions.ipv6. What if I - similarly to the ipv4 setup - don't care about the interface-naming, and just want to enable ipv6?

Or, it feels weird to set node-specific kubelet flags like podCIDR (I think that relates to cluster.network.podSubnets) in the cluster settings of the machineconfig. From my understanding so far, it's more or less expected that the cluster-config is the same on all talos nodes, but the podCIDR can be host-specific... So it'd be nice if there's a more concise documentation on this.

Dualstack with flannel

For a simple example dualstack CNI setup with podCIDR & serviceCIDR.

Dualstack for podCIDR and serviceCIDR with cilium

For cluster-internal networking with podCIDR & serviceCIDR with a more complex CNI.
Since you have explicit cilium docs for other topics, I figure this makes sense as well.

Special case:
In the Cilium kubernetes-ipam docs, I read that the (ipv6) podCIDRs can automatically be set by the hostCIDR - so there's no need for NATing. That sounds too good to be true lol.

Start with the linked Kubernetes dual-stack and kubeadm documentation, then identify the corresponding Talos machine configuration settings. Cover dual-stack nodes and control planes, Flannel, and Cilium pod and service CIDRs, with examples for the requested cases. Done means the documentation clearly explains supported IPv4/IPv6 settings and configuration paths.