SECURITY: OutputPage: Remove separation of css and js module allowance

* No longer segment module origin allowance by an "only=" content
type. Both can be sensitive security-wise and there's no valid
use case for allowing CSS anywhere you want to disallow JS. Both
can significantly impact the user interface and cause unintended
actions to be taken on the user's behalf, or desired actions to
be made practically impossible.

* While at it, also remove the ability to set the module allowance
directly. The reduceAllowedModuleOrigin method is all we need.
I couldn't find usage or mention of setAllowedModules() in
mediawiki-core nor in any other Wikimedia-hosted repository.

Bug: 70672
Change-Id: Icaa75769e9682823bcc9d53f8c917f876705c62a