Add worker nodes.

nix/kubernetes/configuration.nix

@@ -7,6 +7,7 @@
 {
   imports = [
     ./roles/boot
+    ./roles/containerd
     ./roles/control_plane
     ./roles/doas
     ./roles/dont_use_substituters
@@ -24,8 +25,7 @@
     ./roles/ssh
     ./roles/sshd
     ./roles/user
-    ./roles/zfs
-    ./roles/zrepl
+    ./roles/worker_node
     ./roles/zsh
     ./util/install_files
     ./util/unfree_polyfill