Avoid untidy calls to OutputPage::addWikiText()

The OutputPage::addWikiText() method in core is untidy and has been
deprecated in 1.32. Fallback to OutputPage::addWikiTextTitle(),
present since 1.21 or earlier, via a helper to match the tidy output
of the modern OutputPage::addWikiTextAsInterface().

Collect change lines into an array and emit them as once so they
are certain to end up in the same HTML list container element.

Bug: T198214
Change-Id: I737043634d98c65db2ee312c196431681f55dff3