Remove deprecated provider, fix flatcar configs, enable CI tests and refactor hetzner terraform (#10002)

* Remove deprecated provider and fix flatcar configs

* Refactor for DRYness

* Add missing line endings

* Enable tests for hetzner terraform in CI

* Add missing inventory for CI tests

contrib/terraform/hetzner/modules/kubernetes-cluster-flatcar/templates/machine.yaml.tmpl

@@ -1,8 +1,11 @@
----
+variant: flatcar
+version: 1.0.0
+
 passwd:
   users:
     - name: ${user_flatcar}
       ssh_authorized_keys: ${ssh_keys}
+
 storage:
   files:
     - path: /home/core/works