[KDirOperator] Use more human-readable sort order descriptions

Summary: Inspired by D22006

Test Plan:
LANG=EN ctest

Reviewers: ngraham, Frameworks, nicolasfella

Reviewed By: ngraham

Subscribers: churaev, kde-frameworks-devel

Tags: Frameworks

Maniphest Tasks: T8552

Differential Revision: https://phabricator.kde.org/D22763