Properly manage touch events

Call QQuickItem::touchEvent only for unmanaged events, as that implementation will ignore the event, and therefore break the touch management.

Reason for the change

without this only the touch begin arrives, so m_pressAndHoldTimer always trigger, no matter what, always going in edit mode at the minimal touch of the desktop

Test plan

with a touchscreen edit mode on long touch works as wekpected with both desktop and folderview containments