This adds the Integer Math node to shader nodes. It's the same node that
can already be used in Geometry Nodes and the Compositor.
While creating the regression test, I noticed that the integer math
implementation was a bit broken:
* The integer modulo (`%`) operator on the GPU is undefined for negative
divisors (the added regression test showed that the behavior is not
consistent across platforms).
* Use integer power function instead of using float implementation with
casts.
The MaterialX implementation is omitted for now. I didn't look into it
in detail yet but for the Boolean Math node (#162798) it seemed like
some more work is needed there to support this type.
Pull Request: https://projects.blender.org/blender/blender/pulls/163805
