bug#54017: add regexp translation option to read-regexp

[Juri Linkov]

> Suppose, the user wants to use ( ) for capturing and
> \( \) for matching parens. He provides a function
> which does this translation.
>
> If this new option is set and is a function which does
> the translation then read-regexp will
>
> - accept the format which the user prefers, in this case
> ( ... ) for capturing.
>
> - store regexps in this format in history, so the user
> can work with the user's preferred format even when
> retrieving history entries.
>
> - return the elisp format regexp by calling the function
> provided by the user which does the translation.

This user option already exists.  It's name is 'search-default-mode'.
For stand-alone query-replace it's called 'replace-regexp-function'.

So we just need someone to write these regexp translation functions.