vault: 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/vault/test_vault_client_context.yml

@@ -7,7 +7,7 @@
 
   tasks:
   - name: Setup testing environment.
-    import_tasks: env_setup.yml
+    ansible.builtin.import_tasks: env_setup.yml
 
   # vault requires 'ipaapi_context: client', and uses this
   # context by defoult, so we test only for the case where
@@ -22,4 +22,4 @@
     failed_when: not (result.failed and result.msg is regex("Context 'server' for ipavault not yet supported."))
 
   - name: Cleanup testing environment.
-    import_tasks: env_cleanup.yml
+    ansible.builtin.import_tasks: env_cleanup.yml