Regression since ce2f541deb

`--mount` is safer, as `-v` has the side-effect of creating the "source"
destination as a directory if it doesn't exist yet.
We don't need such magic.

* add prometheus-nginxlog-exporter role

* Rename matrix_prometheus_nginxlog_exporter_container_url to matrix_prometheus_nginxlog_exporter_container_hostname

* avoid referencing variables from other roles, handover info using group_vars/matrix_servers

* fix: stop service when uninstalling

fix: typo

move available arch's into a var

fix: text

* fix: prometheus enabled condition

Co-authored-by: ikkemaniac <ikkemaniac@localhost>