Konfigurator: Avoid needing to apply `setWhatsThis()` and `setToolTip()` before…

Authored by asensi on May 14 2020, 11:43 PM.

Description

Konfigurator: Avoid needing to apply setWhatsThis() and setToolTip() before calling createSpinBox()

Modify createSpinBox(...) in order to require a QLabel as an argument,
therefore applying setWhatsThis(toolTip) and setToolTip() to
that QLabel is done automatically (and those steps do not have to
be remembered by developers).

Differential Revision: https://phabricator.kde.org/D29546