Feature: #97326 - Open backend page from admin panel

See forge#97326

Description

In previous versions with EXT:feedit the admin panel had a button to directly open the currently viewed page in the backend. Since we have backend routing available, we can implement a similar feature directly in the admin panel. This will not replace the complete functionality of feedit, but it gives editors a possibility to navigate via the frontend and directly open the backend with a single click.

Impact

The admin panel has a direct link to the corresponding backend page.