[ClusterClass] Allow templating of pod/serviceSubnets and dnsDomain

[nikParasyr]

What would you like to be added (User Story)?

As a operator I would like to be able to template the clusters podSubnet, serviceSubnet and dnsDomain when using clusterClass or/and RunTimeSDK. This will allow to:

• minimize cluster definitions for our users while keeping sane defaults
• validate various cluster subnets together with the infrastructure node subnet via XValidations/CEL/...

Detailed Description

On v1beta1 it was possible to config:

• podSubnet
• serviceSubnet
• dnsDomain
  through: https://pkg.go.dev/sigs.k8s.io/cluster-api@v1.10.4/bootstrap/kubeadm/api/v1beta1#Networking.
  This could be used by clusterClass/runTimeSDK to template these values.

On v1beta2 these fields were removed and the only possible way to configure them is through clusterNetwork. Unfortunately these fields are not "templated" by ClusterClass/RunTimeSDK.

Anything else you would like to add?

This is a continuation of the discussion that occured here

Label(s) to be applied

/kind feature
One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

[k8s-ci-robot]

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