evil-search-forward does not respect new user option search-default-mode, in particular the char-fold-to-regexp setting

Sorry to pedantically quote straight from the 25.1 news file, but I can't say it better myself.

> 'isearch' and 'query-replace' can now perform character folding in matches.
> This is analogous to case folding, but instead of disregarding case
> variants, it disregards wider classes of distinctions between similar
> characters. (Case folding is a special case of character folding.)
> This means many characters in the search string will match entire
> groups of characters instead of just themselves.

> For instance, the ASCII double quote character " will match all
> variants of double quotes, and the letter 'a' will match all of its
> accented cousins, even those composed of multiple characters, as well
> as many other symbols like U+249C (PARENTHESIZED LATIN SMALL LETTER
> A).

> Character folding is enabled by customizing 'search-default-mode' to
> the value 'char-fold-to-regexp'. You can also toggle character
> folding in the middle of a search by typing 'M-s ''.

I took a look at the implementation of `evil-search-forward` but couldn't figure out where to patch it to respect the new `search-default-mode` variable. Happy to take another swing at it if somebody could point me in the right direction!

Start at the evil-search-forward implementation and trace how it selects search behavior, then compare that with Emacs isearch and query-replace handling of search-default-mode. Done means evil-search-forward respects search-default-mode, including char-fold-to-regexp, while preserving the existing search behavior otherwise.

Written by the indexing model from the issue text.