Factor out the four code paths for standardIcon() (windows, mac,
application and resource theme) and use those functions also for
standardPixmap() so the returned pixmap is correctly scaled with the
current devicePixelRatio.
Part 2: move functionality into own functions
Task-number: QTBUG-118122
Change-Id: I0763c4db9e7aecf4c52bf0f5770bd3dd87c4a8a4
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Samuel Gaist <samuel.gaist@idiap.ch>