Ensure users can enable GNOME Shell extensions on Wayland

Currently on Wayland there’s no way to restart GNOME Shell without restarting the full GNOME session, which we don’t support in Tails.

This might be a problem for:

Additional Software that run some stuff before GNOME Shell starts (e.g. parcimonie) or as part of GNOME Shell (e.g. GNOME Shell extensions). We don’t document how to do that currently but such cases might appear after Additional Software has been released officially. For example, I suffer from that with gnome-shell-pomodoro.
Anything else?

Parent Task: #12213

Original created by @sajolida on 15828 (Redmine)

Edited Nov 22, 2019 by intrigeri

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