Avoid incorrect and unecessary menu_link_content entity saving

Neat, we already have the subclass for content_moderation and that fails on 11.x with an exception, as expected. Added the other one too and refactored the code to be similar to core.

Really wish all of this wouldn't be necessary. At least it should only save it once now and we have extensive test coverage.

I think I came to a very similar conclusion ( https://www.drupal.org/project/drupal/issues/3486604 🐛 Node edit form re-saves menu items even if no change has occurred Active ), but then got side-tracked by the rabbit hole of the menu name return issue, I like the self-contained nature of this patch, looks good, I'll try and find the time to give it a test later today on some of our sites.