feat(corfu,vertico): use equal orderless config

This removes the old `&` separator for Vertico (does anyone use that
instead of just space?) in favor of escapable space and unifies
orderless config with Corfu. Also implements smart separator
insert/escape/reset on `C-SPC`

Co-authored-by: Liam Hupfer <liam@hpfr.net>

modules/config/default/config.el

@@ -461,6 +461,7 @@ Continues comments if executed from a commented line. Consults
   (map! :when (modulep! :completion corfu)
         :after corfu
         (:map corfu-map
+         [remap corfu-insert-separator] #'+corfu-smart-sep-toggle-escape
          "C-S-s" #'+corfu-move-to-minibuffer
          "C-p" #'corfu-previous
          "C-n" #'corfu-next