[#699] split k8s platform body of work out of PFVCluster

Framework enforcement layer adopted; shellcheck clean; real kubeconfigs
gitignored (example only in repo). Provenance: PFVCluster/k8s.
https://projects.knownelement.com/issues/699#note-4536

kubeconfig.example.yaml

@@ -0,0 +1,18 @@
+apiVersion: v1
+clusters:
+- cluster:
+    certificate-authority-data: <base64 CA>
+    server: https://100.125.134.53:6443
+  name: pfv-k8s
+contexts:
+- context:
+    cluster: pfv-k8s
+    user: pfv-k8s
+  name: pfv-k8s
+current-context: pfv-k8s
+kind: Config
+users:
+- name: pfv-k8s
+  user:
+    client-certificate-data: <base64 client cert>
+    client-key-data: <base64 client key>