bug#66394: 29.1; Make register-read-with-preview more useful

[Eli Zaretskii]

> From: Thierry Volpiatto <thievol@posteo.net>
> Cc: monnier@iro.umontreal.ca,  michael_heerdegen@web.de,
>   stefankangas@gmail.com,  66394@debbugs.gnu.org
> Date: Sat, 25 Nov 2023 21:14:31 +0000
> 
> Here a patch with the change suggested by Stefan applied, slighly
> modified though because it fails if I put the call to
> cl--generic-prefill-dispatchers at the recommended place.
> 
> I recompiled Emacs with this patch with no errors.

Thanks.

Stefan, any further comments, or should I install this as submitted?