kdirselectdialog: when creating a new dir that already exists, select it
If the user tries to create a new dir and a dir with that name already exists, select the existing dir in the tree view.
Don't use KIO::encodeFileName as it replaces '/' with the unicode character fraction slash, which breaks creating nested dirs.
Drive-by change: port to KIO::setDetails(StatDetails).
Feature: 424082