Force completion in icomplete with C-M-i, but don't cycle (bug#34077)

Force completion in icomplete with C-M-i, but don't cycle (bug#34077)

Cycling after forcing a completion with C-M-i in icomplete can be
confusing, as it leaves rotated prospects in the minibuffer.  In C-x
C-f, for example it is very difficult to understand if the prospects
refer to subdirectories of the directory being completed to, which
happens naturally when the completion is unique; or if they are a
cycled version of prospects that match the new completion pattern, in
case the completion happens to still match other items.

To resolve this confusion, never cycle with C-M-i in icomplete:
non-ambiguous cycling can be achieved with C-. and C-,

The former behaviour can still be restored with:

(define-key icomplete-minibuffer-map (kbd "C-M-i") 'minibuffer-force-complete)

* lisp/icomplete.el (icomplete-force-complete): New command.
(icomplete-minibuffer-map): Bind C-M-i to icomplete-force-complete.