Add ignition nerdctl-full installer

This doesn't actually start any services, but waiting for the
nerdctl user to run `containerd-rootless-setuptool.sh install`.

Alternatively to start up the installed system containerd.service,
replacing the one from docker, and run `sudo nerdctl` with it.

Signed-off-by: Anders F Björklund <anders.f.bjorklund@gmail.com>

examples/experimental/fedora-coreos.yaml

@@ -13,8 +13,3 @@ images:
 mounts:
 - location: "/tmp/lima"
   writable: true
-
-# The built-in containerd installer does not support CoreOS currently.
-containerd:
-  system: false
-  user: false

pkg/cidata/cidata.TEMPLATE.d/ignition.yaml

@@ -61,6 +61,17 @@ systemd:
 
         [Install]
         RequiredBy=multi-user.target
+{{- if or .Containerd.User .Containerd.System }}
+    - name: lima-install-containerd.service
+      enabled: true
+      contents: |
+        [Service]
+        Type=oneshot
+        ExecStart=/bin/sh -c "/usr/bin/tar Cxzf /usr/local /mnt/lima-cidata/nerdctl-full.tgz"
+
+        [Install]
+        RequiredBy=multi-user.target
+{{- end}}
     - name: lima-install-guestagent.service
       enabled: true
       contents: |