user: Use FQCN for ansible.builtin

Use Fully Qualified Collection Name (FQCN) for ansible builtins. This is
ansible.builtin.set_fact instead of set_fact for example and aplies for
all actions that are part of ansible.builtin.

All the replaced ansible.builtins:
  assert, command, copy, debug, fail, fetch, file, import_playbook,
  import_tasks, include_role, include_tasks, include_vars, package,
  set_fact, shell, slurp, stat, systemd

playbooks/user/ensure_user_with_randompassword.yml

@@ -15,5 +15,5 @@
     register: ipauser
 
   - name: Print generated random password
-    debug:
+    ansible.builtin.debug:
       var: ipauser.user.randompassword