bug#10477: zap-to-char should allow picking from history

[Juri Linkov <juri@linkov.net>]

>> zap-to-char should allow typing e.g., the up arrow to pick a recently used
>> character, and then RET.
>>
>> Currently the only way is to type the actual character back in again!
>> Even if hard to type CKS!
>>
>> Currently one gets 'Non-character input-event'.
>
> I've now implemented this in Emacs 27 -- it was more code than expected,
> so perhaps simple.el isn't the right place for it.  On the other hand,
> `zap-to-char' is there, so perhaps that's the right place for it?

I tried typing the up arrow, but it fails with the error
"Non-character input-event".  Is this intentional?

> Or it could go to subr-x.el with an autoload -- `zap-to-char' probably
> isn't the most used command ever, anyway, and I'm not sure
> `read-char-with-history' has much utility outside that command.

Indeed, subr-x.el looks like a more suitable place.

Another variant is create a new file for commands reading input
with a name like read-x.el (or maybe minibuffer-x.el or prompt-x.el).
Then put here `read-char-with-history', also all functions from
lisp/emacs-lisp/map-ynp.el and lisp/emacs-lisp/rmc.el,
maybe also read-char-choice from subr.el.