right now there's no real toon shader, however you can achieve some toon like effects with the skin diffusion shader. if you set the shadow smoothing to zero, you get a super hard edge which can look pretty cool.
Seems possible, especially considering that there is a way to bring these same shading artifacts in Eevee - I did that just by plugging the normal map into an AO node and looking at the isolated diffuse color render pass I have a sneaking suspicion that the AO node may be utilizing Cycles for its raytracing (I doubt that…