REPL: fix yank-twice activates region (#33814)
Yanking twice was fooling `setmark` into believing
that `^Space`, the keybinding for `setmark`, had
been pressed twice, leading to activating the region.
So let's make `setmark` behave as a "command" (and
activate the region) only when called directly by
the user, otherwise treat it as a low-level function.
