bug#51475: read-char-choice should hide the cursor

[Gregory Heytings]

> Perhaps if the user wants this, they could just use 
> `minibuffer-setup-hook' to make the cursor go away?

Indeed, that's yet another solution:

(minibuffer-with-setup-hook
    (lambda () (setq-local cursor-type nil))
  (read-char-choice " a - good\n b - bad\n c - ugly" '(?a ?b ?c)))

But that doesn't work if read-char-choice-use-read-key is non-nil.  And 
given that cursor-in-echo-area is explicitly bound in 
read-char-choice-use-read-key, there's I think no similar trick that could 
be used to make that case work.