Propagate IG NodeLabels to k8s nodes in Hetzner

[rifelpet]

Fixes #16159

This adds Hetzner server labels for the instance group nodeLabels. kops-controller then recognizes these server labels and sets them on the associated k8s node.

I'm marking this WIP as we may need to change this approach due to label length limits in the Hetzner API:

https://docs.hetzner.com/cloud/servers/getting-started/creating-a-server/

Both key and value must be 63 characters or less, beginning and ending with an alphanumeric character and alphanumerics can be used inbetween

The Hetzner CCM mentions support for the node.kubernetes.io/exclude-from-external-load-balancers label included in the integration test output changes: hetznercloud/hcloud-cloud-controller-manager#182 (comment) which is 55 characters on its own, so with the prefix I've added it exceeds the length limit. I considered storing these elsewhere like in userdata and having kops-controller parse them out of the hcloud.Server's userdata, except hcloud doesn't expose userdata in read operations, it is a write-only field.

Therefore I think our only option is to use a shorter prefix

/wip

[rifelpet]

/cc @hakman
any thoughts on how to best approach the length limit issue?

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[hakman]

/test all

[hakman]

/test all

[rifelpet]

/retest

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[hakman]

/test all

[hakman]

/retest

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@rifelpet: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-kops-e2e-k8s-gce-cilium	99c8fb0	link	true	/test pull-kops-e2e-k8s-gce-cilium

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