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_symmetric.yml

@@ -7,7 +7,7 @@
 
   tasks:
   - name: Setup testing environment.
-    import_tasks: env_setup.yml
+    ansible.builtin.import_tasks: env_setup.yml
 
   - name: Ensure symmetric vault is present
     ipavault:
@@ -74,7 +74,7 @@
     failed_when: result.changed or result.failed or (result.vault.data | default(false))
 
   - name: Verify retrieved data.
-    slurp:
+    ansible.builtin.slurp:
       src: "{{ ansible_facts['env'].HOME }}/data.txt"
     register: slurpfile
     failed_when: slurpfile['content'] | b64decode != 'Hello World.'
@@ -351,4 +351,4 @@
     failed_when: result.failed or not result.changed
 
   - name: Cleanup testing environment.
-    import_tasks: env_cleanup.yml
+    ansible.builtin.import_tasks: env_cleanup.yml