CI/molecule: use common vars as well and simplify run (#13520)

The molecule_run.sh isn't really needed since the switch to gitlab-ci
matrix runs.

Also use the inventory variables pattern for kata-containers.

roles/container-engine/kata-containers/molecule/default/molecule.yml

@@ -7,12 +7,16 @@ platforms:
     vm_memory: 1024
     node_groups:
       - kube_control_plane
+      - kube_node
+      - k8s_cluster
   - name: ubuntu24
     cloud_image: ubuntu-2404
     vm_cpu_cores: 1
     vm_memory: 1024
     node_groups:
       - kube_control_plane
+      - kube_node
+      - k8s_cluster
 provisioner:
   name: ansible
   env:
@@ -21,6 +25,11 @@ provisioner:
     defaults:
       callbacks_enabled: profile_tasks
       timeout: 120
+  inventory:
+    group_vars:
+      k8s_cluster:
+        kata_containers_enabled: true
+        container_manager: containerd
   playbooks:
     create: ../../../../../tests/cloud_playbooks/create-kubevirt.yml
     prepare: ../../../molecule/prepare.yml