Avoid accidental scrolling when performing pinch gesture

When starting a pinch the user first touches with one finger. That causes the QScroller to enter the pressed state.
Then when the second finger touches and moves this causes the QScroller to interpret it as a scroll. This causes
the view position of the document to move

To avoid this send InputRelease to the scroller when a pinch starts to make sure it is no longer in pressed state.
Also don't send any input to the scroller while the pinch is ongoing to avoid it entering the pressed state again.

BUG: 421755