馃崚 manually position tooltip so it's correct
Qt tries to reposition when there isn't enough space and gloriously fails. Instead adjust the coordinates such that Qt has no reason to reposition.
since this adds a lot of code we now have a shared shapetooltip item that is used by the centershape and the segmentshape. also correctly set shapeitem as parent for our tooltip (the coordindates are relative to it because our mouseyarea is on top of shapeitem)
(cherry picked from commit 47eaad04)