Fix CAPTCHA on new editors


Fix CAPTCHA on new editors

Previously, the CAPTCHA error showed the raw HTML, and also
there was no way to submit the CAPTCHA.

  • Standardize on onEditorSaveContent
  • Pass specific i18n message related to the spam filter flag to the API response so we know which ones it's safe to treat as HTML.

Bug: T109554
Change-Id: I5df07700540898c7997b9ad0d8c5f81f3b6af721