certbot(role): support DNS-01 certs using acme-dns

Introduce new configuration structure called certbot__certs, which
allows for different challenge types per cert with the first challenge
type supported being dns-01-acme-dns.

roles/certbot/tasks/main/certs.yaml

@@ -1,4 +1,14 @@
-- name: obtain certificates
+- name: obtain http-01 challenge certificates
   loop: "{{ certbot__certificate_domains }}"
+  ansible.builtin.include_tasks:
+    file: main/http_01_cert.yaml
+
+- name: validate certs config
+  loop: "{{ certbot__certs }}"
+  ansible.builtin.include_tasks:
+    file: main/validate_cert.yaml
+
+- name: obtain certs
+  loop: "{{ certbot__certs }}"
   ansible.builtin.include_tasks:
     file: main/cert.yaml