service: 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

tests/service/env_setup.yml

@@ -1,11 +1,11 @@
 # Setup environment for service module tests.
 ---
 - name: Setup variables and facts.
-  include_tasks: env_vars.yml
+  ansible.builtin.include_tasks: env_vars.yml
 
 # Cleanup before setup.
 - name: Cleanup test environment.
-  include_tasks: env_cleanup.yml
+  ansible.builtin.include_tasks: env_cleanup.yml
 
 - name: Add IP address for "nohost" host.
   ipadnsrecord: