Convert RKE2 registries to template, disable default endpoints (#474)

## Summary
- Replace static `registries.yaml` with EPP template driven by `rke2::registries` hash
- Add `disable-default-registry-endpoint: true` to all mirrors — RKE2 will only use artifactapi and never fall back to upstream registries
- Registry configuration now fully managed via hiera data (`roles/infra/k8s.yaml`)

Reviewed-on: #474
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

modules/rke2/files/registries.yaml

@@ -1,38 +0,0 @@
----
-# DO NOT MODIFY - MANAGED BY PUPPET
-mirrors:
-  docker.io:
-    endpoint:
-      - "https://artifactapi.k8s.syd1.au.unkin.net"
-    rewrite:
-      "^(.*)$": "dockerhub/$1"
-  ghcr.io:
-    endpoint:
-      - "https://artifactapi.k8s.syd1.au.unkin.net"
-    rewrite:
-      "^(.*)$": "ghcr/$1"
-  quay.io:
-    endpoint:
-      - "https://artifactapi.k8s.syd1.au.unkin.net"
-    rewrite:
-      "^(.*)$": "quay/$1"
-  registry.k8s.io:
-    endpoint:
-      - "https://artifactapi.k8s.syd1.au.unkin.net"
-    rewrite:
-      "^(.*)$": "k8s-registry/$1"
-  registry.gitlab.com:
-    endpoint:
-      - "https://artifactapi.k8s.syd1.au.unkin.net"
-    rewrite:
-      "^(.*)$": "gitlab/$1"
-  docker.elastic.co:
-    endpoint:
-      - "https://artifactapi.k8s.syd1.au.unkin.net"
-    rewrite:
-      "^(.*)$": "elastic/$1"
-  gcr.io:
-    endpoint:
-      - "https://artifactapi.k8s.syd1.au.unkin.net"
-    rewrite:
-      "^(.*)$": "gcr/$1"