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)

roles/network_facts/defaults/main.yml

@@ -0,0 +1,5 @@
+---
+# Additional string host to inject into NO_PROXY
+additional_no_proxy: ""
+additional_no_proxy_list: "{{ additional_no_proxy | split(',') }}"
+no_proxy_exclude_workers: false