[PFO] Filtering Word-related and superfluous styles and classes

[Reinmar]

Part of #10577.

• Order of processing the content
  1. inline stylesheets
  2. normalization (lists, images, etc)
  3. filter word-related and superfluous content (has to be done after normalization because normalization may require this information)
  4. inline block styles to text
• Scope:
  • Review existing CKE4's implementation for what needs to be removed. You can find these things also in the original PoC, but that implementation was rather poor.
  • Mso* classes.
  • <span style="mso-ansi-language:PL;" lang="PL">Bar</span> if the language is different than [editor.language.content](<https://ckeditor.com/docs/ckeditor5/latest/api/module_core_editor_editorconfig-LanguageConfig.html#member-content>) (it may require some smarter comparison method because of different language name formats).

[wimleers]

Also reported over in Drupal 9.3: https://www.drupal.org/project/drupal/issues/3254346

[CKEditorBot]

There has been no activity on this issue for the past year. We've marked it as stale and will close it in 30 days. We understand it may be relevant, so if you're interested in the solution, leave a comment or reaction under this issue.

[CKEditorBot]

We've closed your issue due to inactivity over the last year. We understand that the issue may still be relevant. If so, feel free to open a new one (and link this issue to it).

[Reinmar]

This issue was actually resolved with #14925.