[3.0.x] Children block not rendering children in Layout Builder

I encountered a similar issue when placing paragraphs as an entity reference into a Menu Extra Item field. The paragraphs would render when logged in as an admin, but disappeared when logged out.

Re-rolling part of the branch as a patch that we're using to fix that issue.

Ran in to comment 4's issue today and this patch fixes our issues - thank you!

@pschuelke and @ChristianSanders your particular issue of access was addressed at the end of the linked issue here https://www.drupal.org/project/menu_item_extras/issues/3167363#comment-1... 🐛 Children block not rendering children in Layout Builder Needs review

This ticket is not about access, this is about the issue with double rendering of the menu item extras because of being in preprocess vs an entity build.

This ticket is actually also just a different branch version for 🐛 Children block not rendering children in Layout Builder Needs review . If you do a re-roll of the code here it should be all the code I included, or, if it's not, it should be addressed in another ticket.

This issue is already very confusing, with this new patch it's now buried what the original intent of my code was.

Rebase onto 3.1.x.