Regression (5-6): memory usage of QPointerEvent and QEventPoints

In Qt 6 QMouseEvent inherits from QPointerEvent, which has a

    QList<QEventPoint> m_points;

member.

In turn, QEventPoint is a pimpl (think) class.

This means that for each mouse event one pays for 2 memory allocations, on top of the (eventual) allocation for the mouse event itself.

In the super common case for a desktop application this is 3x the number of heap allocations required (and that were done in Qt 5 anyhow).