Qt relies on event timestamp information to detect double click events.
The information was not passed through QGraphicsSceneEvent, so the
synthesized QMouseEvent delivered for the second press of a double click
to an embedded widget was never recognized as a double click.
This requires addition of a new setter/getter to QGraphicsSceneEvent.
Event though not all QGraphicsSceneEvent instances will have a valid
timestamp, this provides us with more flexibility than adding the API to
several QGraphicsSceneEvent types (mouse, touch, wheel).
Pick-to: 6.2
Fixes: QTBUG-96009
Change-Id: I343f25902286157f6d6670641dfad9c92dd44250
Reviewed-by: Lars Knoll <lars.knoll@qt.io>