Extend fuzz test to cover render target

The "parse" target doesn't reach the render pipeline. Add a "render"
target which drives registerAnimator() and the raster paint path, so
libFuzzer can reach that code.

Task-number: QTBUG-139707
Change-Id: If82a16cc7dce9be57de9672e58fbacdf7364fa6e
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>