feat(staging): Rename flux/cluster to cluster/config

This is a multi-step process collapsed into a single commit

* set prune=false for flux/cluster, then deploy
* add empty kustomization to cluster/config and point
  flux-system/flux-operator/instance at it, then deploy
* move cluster.yaml to cluster/config, then deploy
* set prune=true

kubernetes/staging/apps/flux-system/flux-operator/instance/helm-values.yaml

@@ -14,7 +14,7 @@ instance:
     kind: GitRepository
     url: https://github.com/szinn/k8s-homelab.git
     ref: refs/heads/main
-    path: kubernetes/staging/flux/cluster
+    path: kubernetes/staging/cluster/config
   commonMetadata:
     labels:
       app.kubernetes.io/name: flux

kubernetes/staging/cluster/settings/kustomization.yaml

@@ -0,0 +1,6 @@
+---
+# yaml-language-server: $schema=https://json.schemastore.org/kustomization
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+namespace: flux-system
+resources: []