proxy: Fix the no_proxy variable (#12981)

* CI: add no_proxy regression test

* proxy: Fix the no_proxy variable

Since 2.29, probably due to a change in ansible templating, the no_proxy
variable is rendered as an array of character rather than a string.

This results in broken cluster in some case.

Eliminate the custom jinja looping to use filters and list flatteing +
join instead.
Also simplify some things (no separate tasks file, just use `run_once`
instead of delegating to localhost)

playbooks/internal_facts.yml

@@ -16,6 +16,8 @@
     - name: Gather and compute network facts
       import_role:
         name: network_facts
+      tags:
+        - always
     - name: Gather minimal facts
       setup:
         gather_subset: '!all'