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-nginx-proxy/vars/main.yml

@@ -0,0 +1,18 @@
+---
+
+# Tells whether this role had executed or not. Toggled to `true` during runtime.
+matrix_nginx_proxy_role_executed: false
+
+matrix_ssl_renewal_systemd_units_list:
+  - name: matrix-ssl-lets-encrypt-certificates-renew.service
+    applicable: "{{ matrix_ssl_retrieval_method == 'lets-encrypt' }}"
+    enableable: false
+  - name: matrix-ssl-lets-encrypt-certificates-renew.timer
+    applicable: "{{ matrix_ssl_retrieval_method == 'lets-encrypt' }}"
+    enableable: true
+  - name: matrix-ssl-nginx-proxy-reload.service
+    applicable: "{{ matrix_ssl_retrieval_method == 'lets-encrypt' and matrix_nginx_proxy_enabled | bool }}"
+    enableable: false
+  - name: matrix-ssl-nginx-proxy-reload.timer
+    applicable: "{{ matrix_ssl_retrieval_method == 'lets-encrypt' and matrix_nginx_proxy_enabled | bool }}"
+    enableable: true