icomplete-vertical simplest approach

* lisp/icomplete.el (icomplete--vertical-prospects) : New functions to
assert format and correct number of candidates in vertical format.
(icomplete--horizontal-prospects) : New functions to assert format and
correct number of candidates in horizontal format.
(icomplete-minibuffer-setup-hook) : Conditionally initialize the
variables for vertical format.
(icomplete-completions) : Simplify to separate some calculations
unneeded in vertical format. Moved part of its code to
icomplete--horizontal-prospects.
2 jobs for feature/icomplete-vertical in 78 minutes and 37 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Test
failed #7891
test-filenotify-gio

01:18:37

passed #7892
test-gnustep

01:15:10

 
Name Stage Failure
failed
test-filenotify-gio Test
  SKIPPED  file-notify-test10-sufficient-resources-remote

Makefile:177: recipe for target 'lisp/filenotify-tests.log' failed
make[1]: Leaving directory '/builds/emacs/emacs/test'
make[1]: *** [lisp/filenotify-tests.log] Error 1
Makefile:243: recipe for target 'lisp/filenotify-tests' failed
make: Leaving directory '/builds/emacs/emacs/test'
make: *** [lisp/filenotify-tests] Error 2
ERROR: Job failed: exit code 1