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/templates/synapse/ext/s3-storage-provider/env.j2

@@ -0,0 +1,11 @@
+AWS_ACCESS_KEY_ID={{ matrix_synapse_ext_synapse_s3_storage_provider_config_access_key_id }}
+AWS_SECRET_ACCESS_KEY={{ matrix_synapse_ext_synapse_s3_storage_provider_config_secret_access_key }}
+AWS_DEFAULT_REGION={{ matrix_synapse_ext_synapse_s3_storage_provider_config_region_name }}
+
+ENDPOINT={{ matrix_synapse_ext_synapse_s3_storage_provider_config_endpoint_url }}
+BUCKET={{ matrix_synapse_ext_synapse_s3_storage_provider_config_bucket }}
+STORAGE_CLASS={{ matrix_synapse_ext_synapse_s3_storage_provider_config_storage_class }}
+
+MEDIA_PATH=/matrix-media-store-parent/{{ matrix_synapse_media_store_directory_name }}
+
+UPDATE_DB_DURATION={{ matrix_synapse_ext_synapse_s3_storage_provider_update_db_day_count }}d