Deprecate and ignore the riverctl commands for creating explicit
keyboard groups.
In my mind, the only reason to have more than one keyboard group is if
different keyboard devices are assigned different keymaps or repeat
rates. River does not currently allow such things to be configured
however.
When river eventually makes it possible to configure different keymaps
and repeat rates per keyboard device, there is no reason we can't 100%
automatically group keyboards based on the keymap/repeat rate.
Exposing this keyboard group abstraction to the user is just bad UX.
Failing to group keyboards automatically also creates confusing/buggy
behavior for the user if the hardware, for example, exposes some of the
the XF86 buttons on a laptop as a separate keyboard device from the main
keyboard. Creating keybindings for these XF86 buttons that use modifiers
doesn't work by default, but there's no reason it shouldn't just work.
Closes: https://codeberg.org/river/river/issues/1138
46f77f30dc