Set the default_language as cookie and reload the page so that
the spectator can immediately see the language change in effect.
We can reload the page forcefully for spectators since there is
no chance of any work being lost. It is possible that the spectator
may lose the selected message on doing so.
This requires a new dependency, to be able to set cookies from
frontend JavaScript.
Fixes#21961
This revised globe icon avoids looking like a "language choice" icon
(as the previous one did), while still being recognizably Earth (and
not a disk with some things drawn on it) and not showing only North
America (a flaw with the Font Awesome 4.7 icon).
Used a derivative of icon from
https://unpkg.com/ionicons@5.5.2/dist/svg/earth.svg
with modified outline by Vlad Korobov.