keyboard: Add extended keys and language popups to top window group

keyboard: Add extended keys and language popups to top window group

As per commit 2bd80579ed important actors are added to the top window group
using the layout's addTopChrome method.

This group includes the on-screen keyboard, however its popups were not added
and so they are now shown under the OSK and don't receive any input.

Fix this by adding Language popup and extended keys popup to top chrome.

Fixes https://gitlab.gnome.org/GNOME/gnome-shell/issues/1396
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/583