When calling setSceneRect() on a QTouchPoint it will cause the
ellipseDiameters to be changed, whereas this should not be affected by
the scene rectangle as it should be in logical pixels.
Also add a manual test for visually checking the ellipse diameters on
various devices.
Change-Id: I1ee9207cb1a63cfef33fe904594c73aba221af5c
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
