Add role for ensuring system is updated and potentially rebooted

The role also cleans up the local repository of retrieved package files
that can no longer be downloaded.

playbooks/roles/system_update/handlers/main.yaml

@@ -0,0 +1,5 @@
+# Reboot to apply potentially outstanding kernel updates and make sure all the
+# latest versions of libraries are used.
+- name: Reboot, if stuff changed, for good measure
+  ansible.builtin.reboot:
+  become: true