Fixes #37002 - Add pagelet anchor for user and usergroup tabs

[bastian-src]

Allow plugins to add pagelets for the users/usergroups edit page.

I'm currently working on a plugin that is about to add an attribute to the users/usergroups model and such attribute shall be modifiable on the corresponding edit pages. Therefore, I would like to add such anchor for pagelet rendering.

Suggestions/feedback is welcome :)