Hard deprecate non-tidy OutputPage::addWikiText() method
Tidy will always be enabled with our future parsers. Hard-deprecate
this method which doesn't tidy the output.
Users of `OutputPage::addWikiText()` will be converted one-by-one to
`OutputPage::addWikiTextAsInterface()` so that any unexpected issues
(deliberately untidy wikitext added, which should be rare) can be
addressed.
Bug: T198214
Depends-On: I778ba9e6efed576605f492c9a073c7203b6c0477
Depends-On: I16529879a3b3aed960c5dc006e2af513d7e91fcd
Change-Id: If8353c37245d9d233d589f82c198668ccb3fce05