tests/external-signed-ca-*: 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/external-signed-ca-with-automatic-copy/install-server-with-external-ca-with-automatic-copy.yml

@@ -15,7 +15,7 @@
 
   tasks:
   - name: Run external-ca.sh
-    command: >
+    ansible.builtin.command: >
       /bin/bash
       external-ca.sh
       "{{ groups.ipaserver[0] }}"

tests/external-signed-ca-with-manual-copy/install-server-with-external-ca-with-manual-copy.yml

@@ -11,7 +11,7 @@
 
   post_tasks:
   - name: Copy CSR /root/ipa.csr from node to "{{ groups.ipaserver[0] + '-ipa.csr' }}"
-    fetch:
+    ansible.builtin.fetch:
       src: /root/ipa.csr
       dest: "{{ groups.ipaserver[0] + '-ipa.csr' }}"
       flat: yes
@@ -21,7 +21,7 @@
 
   tasks:
   - name: Run external-ca.sh
-    command: >
+    ansible.builtin.command: >
       /bin/bash
       external-ca.sh
       "{{ groups.ipaserver[0] }}"
@@ -38,7 +38,7 @@
 
   pre_tasks:
   - name: Copy "{{ groups.ipaserver[0] + '-chain.crt' }}" to /root/chain.crt on node
-    copy:
+    ansible.builtin.copy:
       src: "{{ groups.ipaserver[0] + '-chain.crt' }}"
       dest: "/root/chain.crt"
       force: yes