Handle kube-proxy v1alpha2 migration

[sbueringer]

the kube-proxy v1alpha2 is planned for release in 1.31.
@neolit123 kubernetes/kubeadm#1681 (comment)

Sooner or later we have to figure out what we should do about it in core CAPI.

[k8s-ci-robot]

This issue is currently awaiting triage.

If CAPI contributors determine this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[sbueringer]

Very likely not blocking for Kubernetes 1.31 support in CAPI, but I linked it in #10653 so we have it on the radar for 1.31.

[sbueringer]

/cc @neolit123 @fabriziopandini @chrischdi

[neolit123]

/kind feature cleanup
/priority important-longterm

[neolit123]

as discussed quickly with @chrischdi we might have to fork the kube-proxy converters that reside in k/k (not staging) to capi's repo.

i personally don't like this, but the alternative which kubeadm will do, upconvert the config in the kube-proxy cm by calling kube-proxy in a container, might be less appealing to capi.