[ChangeLog][QtCore][QObject] Fixed a bug in setProperty() that caused a
property change not to take effect if the old value compared equal using
QVariant's equality operator, but the values were not strictly equal.
Task-number: QTBUG-69744
Change-Id: I00e04a465fcf4fc1a462fffd1547885861a07a64
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>