cs_keyboard: Add an XKB options page. (#13343)

- Use gnome-xkb-info to populate groups and option lists.
- Translations for these are provided if system language packs are
  installed.
- Some 'grp' ('Switching to another layout') options are forbidden,
  as they lack support in muffin currently.
- Adding or removing 'grp' options will also trigger a Cinnamon
  restart.
- Using 'grp' options is currently unsupported in Wayland sessions -
  use the Cinnamon-style keybindings instead (from the Layouts tab).

Author: mtwebster