Re-add DBus test
Summary:
Ported from KProcess::startDetached to a QProcess we can kill should the
window not exit when closed.
On the KDE CI where the window isn't quitting on close the test might
fail, but it will give us output where we can investigate.
Test Plan: Passes locally
Reviewers: Konsole, Frameworks, hindenburg
Reviewed By: Konsole, hindenburg
Subscribers: hindenburg, konsole-devel
Tags: Konsole
Differential Revision: https://phabricator.kde.org/D16919