This allows to set up everything first - without paying for the layout
calculation at every step - and only then trigger the layout once.
Results:
0.065 msecs to create a QGraphicsTextItem with some text (layouted)
0.036 msecs to set everything up in a QGraphicsTextItem with 0 width
Change-Id: I138bd1d58941d029bc0a36d2730216778f1fbd97
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>