Documents organization setting that configures what message edit
history can be viewed: content edits and topic/channel moves, only
topic/channel moves, or disabling viewing edit history completely.
Renames article to match new help article header and creates URL
redirect for previous article header.
Also, clean up and consolidate related articles.
Fixes#33684.
Co-authored-by: Alya Abbott <alya@zulip.com>
These files are not Jinja2 templates, so there's no reason that they needed
to be inside `templates/zerver`. Moving them to the top level reflects their
importance and also makes it feel nicer to work on editing the help center content,
without it being unnecessary buried deep in the codebase.
