Add Pantalaimon support

This is actually authored by Julian Foad here
(https://lab.trax.im/matrix/matrix-docker-ansible-deploy), but was in
need of a rebase and various adjustments caused by huge playbook
refactoring that landed in the past months.

This rework is completely untested.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/266

setup.yml

@@ -123,6 +123,7 @@
     - custom/matrix-static-files
     - custom/matrix-coturn
     - custom/matrix-media-repo
+    - custom/matrix-pantalaimon
 
     - role: galaxy/auxiliary