title: draw multiple points with different colors in a QQuickItem
body: <p>i want to render a plot with a lot of points (>1.000.000) and different colors in a custom <code>QQuickItem</code>. </p>
  
  <p>Later I want to animate these Points (fading between coordinates and colors), so I think <code>QQuickPaintedItem</code> is not fast enough for this and I must using the <code>updatePaintNode</code> interface of <code>QQuickItem</code>.</p>
  
  <p>The problem is to set the color for each point. Must I create for each Point a <code>QSGGeometryNode</code> and add Geometry and ColorMaterial? Or is there a faster solution?</p>
  
  <p>Best Regards</p>