ApiParsoidTrait depends on some ApiBase methods, which is inconvenient
when one wishes to access Parsoid HTML outside of the action API. Move
the bulk of the code into a new class ParsoidHelper, which doesn't.
Replace the uses of methods:
* dieWithError: throw a different kind of exception where it makes
sense, or change the method to return a StatusValue instead of
throwing where it doesn't
* getPageLanguage: use Title::getPageLanguage() or pass as parameter
* getConfig: pass to constructor
* getLogger: pass to constructor
* getRequest: pass the only required part to constructor,
leave some other API-specific code using it in ApiParsoidTrait
Bug: T314565
Change-Id: I90656cc74bb1cb1f2f3c82ad51cfb164cb8a4a4b
