When air-gapped, specify exactly what needs to be no_proxy'ed

**What would you like to be added**:

I'd like to have specified in the documentation *exactly* what needs to be put into a no_proxy config when running my air-gapped environment. I get that images needs to be pulled, but what other communication when deploying a cluster will hard fail when routed through a proxy? Now it's trial and error only.

**Why is this needed**:

It takes un-nessesarily long time to deploy a cluster when you have to restart the process multiple times to figure out why things silently just hangs, waiting to go through a proxy when it should be routed into the cluster itself.

No files, tests, or entry points are named. Start by tracing the cluster deployment communication paths that can be affected by a proxy in an air-gapped environment, then document the required no_proxy configuration. Done means the documentation identifies all required exclusions and removes the current trial-and-error process.

Written by the indexing model from the issue text.