Move roles/matrix* to roles/custom/matrix*

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.

roles/custom/matrix-coturn/tasks/main.yml

@@ -0,0 +1,23 @@
+---
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/init.yml"
+  tags:
+    - always
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/validate_config.yml"
+  when: "run_setup | bool and matrix_coturn_enabled | bool"
+  tags:
+    - setup-all
+    - setup-coturn
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/setup_install.yml"
+  when: "run_setup | bool and matrix_coturn_enabled | bool"
+  tags:
+    - setup-all
+    - setup-coturn
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/setup_uninstall.yml"
+  when: "run_setup | bool and not matrix_coturn_enabled | bool"
+  tags:
+    - setup-all
+    - setup-coturn