Port from QFontMetrics::width() to boundingRect().width()
In all the cases that were changed, the bounding rect is needed. A few
places were not ported, since they need more careful investigation.
This reduces deprecation warnings.
Reviewers: Konsole, hindenburg
Reviewed By: Konsole, hindenburg
Subscribers: hindenburg, konsole-devel
Differential Revision: https://phabricator.kde.org/D23144