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/completion/corfu/autoload.el

@@ -8,3 +8,18 @@
   (let ((completion-extra-properties corfu--extra)
         (completion-cycle-threshold completion-cycling))
     (apply #'consult-completion-in-region completion-in-region--data)))
+
+;;;###autoload
+(defun +corfu-smart-sep-toggle-escape ()
+  "Insert `corfu-separator' or toggle escape if it's already there."
+  (interactive)
+  (cond ((and (char-equal (char-before) corfu-separator)
+              (char-equal (char-before (1- (point))) ?\\))
+         (save-excursion (delete-char -2)))
+        ((char-equal (char-before) corfu-separator)
+         (save-excursion (backward-char 1)
+                         (insert-char ?\\)))
+        (t
+         ;; Without this corfu quits immediately.
+         (setq this-command #'corfu-insert-separator)
+         (call-interactively #'corfu-insert-separator))))