[Feature Request]: Versionize `system-upgrade-controller` version

[pat-s]

Description

Currently hard-coded in https://github.com/kube-hetzner/terraform-hcloud-kube-hetzner/blob/0c87d28700a8e86f5012961284af6a0d5b29116f/locals.tf#L112 (and hence likely forgotten to upgrade periodically).

Suggestions:

• Expose via variable so users can version it within kube.tf without having to edit the deployment
• Add support for dependabot updates