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/templates/nginx/conf.d/nginx-http.conf.j2

@@ -0,0 +1,14 @@
+#jinja2: lstrip_blocks: "True"
+# The default is aligned to the CPU's cache size,
+# which can sometimes be too low to handle our 2 vhosts (Synapse and Element).
+#
+# Thus, we ensure a larger bucket size value is used.
+server_names_hash_bucket_size 64;
+
+{% if matrix_nginx_proxy_http_level_resolver %}
+	resolver {{ matrix_nginx_proxy_http_level_resolver }};
+{% endif %}
+
+{% for configuration_block in matrix_nginx_proxy_proxy_http_additional_server_configuration_blocks %}
+	{{- configuration_block }}
+{% endfor %}