With these changes, we:

- install https://github.com/Tecnativa/docker-socket-proxy via the
  https://github.com/devture/com.devture.ansible.role.container_socket_proxy Ansible role

- make Traefik access the Docker API via TCP by connecting to this
  socket proxy

- .. which allows us to run the Traefik container with less privileges
  (non-`root`, dropped capabilities)

This new role also adds native Traefik support and support for other
(non-`amd64`) architectures via self-building.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2532

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2522

The newly extracted role also has native Traefik support,
so we no longer need to rely on `matrix-nginx-proxy` for
reverse-proxying to Ntfy.

The new role uses port `80` inside the container (not `8080`, like
before), because that's the default assumption of the officially
published container image. Using a custom port (like `8080`), means the
default healthcheck command (which hardcodes port `80`) doesn't work.
Instead of fiddling to override the healthcheck command, we've decided
to stick to the default port instead. This only affects the
inside-the-container port, not any external ports.

The new role also supports adding the network ranges of the container's
multiple additional networks as "exempt hosts". Previously, only one
network's address range was added to "exempt hosts".

Wiring happens via `group_vars/matrix_servers` now.

Supersedes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2472

With this, other roles (like Coturn, Postmoogle) will be able
to use SSL certificates extracted from Traefik
via https://github.com/ldez/traefik-certs-dumper