Sort Ibuffer filename/process column as displayed

* lisp/ibuf-ext.el (ibuffer-do-sort-by-filename/process): Use the
same function for sorting and for displaying the
filename/process (Bug#45800).

Copyright-paperwork-exempt: yes
3 jobs for master in 8 minutes and 1 second (queued for 3 seconds)
Status Job ID Name Coverage
  Fast
passed #10786
test-fast-inotify

00:06:18

 
  Normal
passed #10787
test-lisp-inotify

00:01:43

passed #10788
test-lisp-net-inotify

00:01:22