Rename ansible groups to use _ instead of - (#7552)

* rename ansible groups to use _ instead of -

k8s-cluster -> k8s_cluster
k8s-node -> k8s_node
calico-rr -> calico_rr
no-floating -> no_floating

Note: kube-node,k8s-cluster groups in upgrade CI
      need clean-up after v2.16 is tagged

* ensure old groups are mapped to the new ones

contrib/terraform/gcp/generate-inventory.sh

@@ -65,12 +65,12 @@ for name in "${MASTER_NAMES[@]}"; do
 done
 
 echo ""
-echo "[kube-node]"
+echo "[kube_node]"
 for name in "${WORKER_NAMES[@]}"; do
   echo "${name}"
 done
 
 echo ""
-echo "[k8s-cluster:children]"
+echo "[k8s_cluster:children]"
 echo "kube_control_plane"
-echo "kube-node"
+echo "kube_node"