Admin bar language switcher in admin area

On the current develop branch, you can use the language switcher in the admin bar to change the locale context for editing; i.e. view all German post translations on the `wp-admin/edit.php` list table. I think this should not be possible, and that the admin bar language switcher should not be available in the admin area now we have admin UI localisation using the UI in the user profile page.

Steps to reproduce:
1. Visit the admin area > All Posts
2. In the admin bar hover the selector indicating the current language (probably the site canonical language), and pick another language
3. You should see the posts displayed change to the post translations for the language you selected

Reproduce the issue from the listed steps on the develop branch, starting at the admin bar language selector on the All Posts screen. Trace where the selector is added in the admin area and compare it with the user profile language UI; done means the admin bar switcher is unavailable in wp-admin while the described profile-based localization remains usable.

Written by the indexing model from the issue text.