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/templates/registries.yaml.epp

@@ -0,0 +1,20 @@
+<%- | Hash $registries | -%>
+---
+# DO NOT MODIFY - MANAGED BY PUPPET
+mirrors:
+<%- $registries.each |$registry, $config| { -%>
+  <%= $registry %>:
+    endpoint:
+<%- $config['endpoint'].each |$ep| { -%>
+      - "<%= $ep %>"
+<%- } -%>
+<%- if $config['rewrite'] { -%>
+    rewrite:
+<%- $config['rewrite'].each |$pattern, $replacement| { -%>
+      "<%= $pattern %>": "<%= $replacement %>"
+<%- } -%>
+<%- } -%>
+<%- if $config['disable-default-registry-endpoint'] { -%>
+    disable-default-registry-endpoint: true
+<%- } -%>
+<%- } -%>