This already returns safe Message objects, which allow Special:Gadgets
to localise it accordingly.
Avoid formatting the list ahead of time with a hardcoded user language,
and instead use Message::listParam() so that the caller controls
the Language object. This makes it safe to use in jobs, CLI, tests,
load.php and elsewhere instead of previously where RequestContext would
cause an exception or use something the caller doesn't control.
Bug: T298334
Change-Id: I77dd3c7fef86b4c8c41837bfb276b019f30baeb0
