CI: streamline packet jobs definition

- Take advantage of `parallel:matrix` to make the jobs definition shorter
  and more readable.
- Remove helper scripts which are no longer needed
- Remove redundant indirection in the gitlab-ci pipelines definitions
  (only one user)

tests/files/debian11-calico-upgrade-once.yml

@@ -0,0 +1,15 @@
+---
+# Instance settings
+cloud_image: debian-11
+
+# Kubespray settings
+download_run_once: true
+
+# Pin disabling ipip mode to ensure proper upgrade
+ipip: false
+calico_pool_blocksize: 26
+calico_vxlan_mode: Always
+calico_network_backend: bird
+
+# Needed to bypass deprecation check
+ignore_assert_errors: true