bug#59486: completion-auto-wrap disobeyed by vertical navigation

[Juri Linkov]

> And here are the corresponding commands for navigating
> the completions buffer from the minibuffer:
>
> +(defun minibuffer-next-line-completion (&optional n)
> +(defun minibuffer-previous-line-completion (&optional n)

It seems there commands can't be bound in the minibuffer.
Ideally, these keybindings could be added to
minibuffer-local-completion-map:

  "M-<left>"  #'minibuffer-previous-completion
  "M-<right>" #'minibuffer-next-completion
  "M-<up>"    #'minibuffer-previous-line-completion
  "M-<down>"  #'minibuffer-next-line-completion

But maybe 'M-<left>' and 'M-<right>' can't be taken from moving by words
even when 'C-<left>' and 'C-<right>' are duplicate keys that are doing
the same.  Or to bind 'M-<left>' and 'M-<right>' only in
completion-in-region-mode-map that is more transient by nature
and is active only as long as the completions buffer is shown.