refactor(publick8s,privatek8s) define infraciadmin SA with a terraform module

[dduportal]

Ref. jenkins-infra/helpdesk#3679

Same as jenkins-infra/digitalocean#134 + jenkins-infra/digitalocean#136 but for Azure

Please note that the privatek8s SA can be used directly by the pod of jenkins-infra/kubernetes-management by mounting the token in the pod directly.

[dduportal]

Plan: 6 to add, 0 to change, 0 to destroy.

with the first inital plan.

I'm gonna import the existing resources, report here and run again the plan, before setting the PR as ready for review

[dduportal]

Report after imports

• publick8s
  • SA already existing: imported, should not change
  • ClusterRoleBinding existing: imported, should not change
  • Token already existing but with another name: imported but should be recreated (breaking effectively the builds of kubernetes-management until the kubeconfig is changed both manually and as code in sops
• privatek8s nothing existing: gotta be created by this PR once merged

[dduportal]

• Build number 655 removed the imported resources before this PR was merged:
  • Before, I was expecting 4 resources to create + 1 to delete (3 creates for private, 1 re-create for public)
  • After, 6 resource to be created from scratch
  • Note: it breaks kube management until credentials are updated
• Build number 657 created the 6 resources successfully