Rename QQuickItem::geometryChanged to geometryChange

https://doc.qt.io/qt-5/qquickitem.html

The convention in Qt Quick and Qt Quick Controls 2 is to use "nounChange" for virtual functions that should handle some change, and "nounChanged" for signals that notify objects of that change.

geometryChanged does not follow that convention:

virtual void geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)

compare that to itemChange:

virtual void itemChange(QQuickItem::ItemChange change, const QQuickItem::ItemChangeData &value)

Not only would renaming geometryChanged to geometryChange allow us to fix this inconsistency, but it would also allow us to add a geometryChanged signal as a public API (item change listeners are private) for listening to geometry changes in an item without listening to all individual x/y/width/height properties: QTBUG-83050