Bullseye Compatibility

So far only some cleanup and added variables for bullseye around explicit version checks that were already in place. Probably needs further changes for full compatibility, so leaving as WIP for now. Esp. thinking of python2 here. This includes some basic changes, esp. needed for our first migrations. Further changes to be expected as we move more hosts to bullseye.

webserver/vars/bullseye.yml

+---
+# yamllint disable rule:line-length
+
+protocols:
+  modern: 'TLSv1.3'
+  intermediate: 'TLSv1.2 TLSv1.3'
+ciphers:
+  modern: null
+  intermediate: 'ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384'
+prefer_server_ciphers:
+  modern: false
+  intermediate: false