Refactor formatter (#17828)

* Refactor formatter

* Move custom emoji pre-rendering logic to view helpers

* Move more methods out of Formatter

* Fix code style issues

* Remove Formatter

* Add inline poll options to RSS feeds

* Remove unused helper method

* Fix code style issues

* Various fixes and improvements

* Fix test

app/controllers/api/web/embeds_controller.rb

@@ -15,7 +15,7 @@ class Api::Web::EmbedsController < Api::Web::BaseController
     return not_found if oembed.nil?
 
     begin
-      oembed[:html] = Formatter.instance.sanitize(oembed[:html], Sanitize::Config::MASTODON_OEMBED)
+      oembed[:html] = Sanitize.fragment(oembed[:html], Sanitize::Config::MASTODON_OEMBED)
     rescue ArgumentError
       return not_found
     end