feat(corfu): general move-to-minibuffer impl

We relied directly on consult for this, meaning it needed the vertico
module. Now, it should defer to the user's choice, including helm, ivy
and ido. Note the convention for this indirection is using the
`completing-read` API, which all such packages implement. This diverges
from Corfu's suggestion of `completion-in-region`, which only vertico
and ivy seem to implement.

modules/completion/corfu/autoload.el

@@ -10,12 +10,13 @@
 
 ;;;###autoload
 (defun +corfu-move-to-minibuffer ()
-  ;; Taken from corfu's README.
-  ;; TODO: extend this to other completion front-ends.
+  ;; Adapted from Corfu's README.
   (interactive)
-  (let ((completion-extra-properties corfu--extra)
-        (completion-cycle-threshold completion-cycling))
-    (apply #'consult-completion-in-region completion-in-region--data)))
+  (pcase completion-in-region--data
+    (`(,_ ,_ ,table ,pred ,extras)
+     (let ((completion-extra-properties extras)
+           completion-cycle-threshold completion-cycling)
+       (completing-read "Completion: " table pred nil nil 'corfu-history)))))
 
 ;;;###autoload
 (defun +corfu-smart-sep-toggle-escape ()

modules/completion/corfu/config.el

@@ -33,6 +33,8 @@
         tab-always-indent (if (modulep! +tng) 'complete tab-always-indent))
   (add-to-list 'completion-category-overrides `(lsp-capf (styles ,@completion-styles)))
 
+  (add-to-list 'corfu-continue-commands #'+corfu-move-to-minibuffer)
+
   (add-hook! 'minibuffer-setup-hook
     (defun +corfu-enable-in-minibuffer ()
       "Enable Corfu in the minibuffer if `completion-at-point' is bound."