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-synapse/tasks/ext/ldap-auth/setup.yml

@@ -0,0 +1,12 @@
+---
+
+- ansible.builtin.set_fact:
+    matrix_synapse_password_providers_enabled: true
+
+    matrix_synapse_additional_loggers: >
+      {{
+        matrix_synapse_additional_loggers
+       +
+        [{'name': 'ldap_auth_provider', 'level': 'INFO'}]
+      }}
+  when: matrix_synapse_ext_password_provider_ldap_enabled | bool