Blender Git Loki

Geometry Nodes: Add operation setting to attribute randomize node

This commit adds a drop-down to the attribute randomize node to support
a few operations on the values of existing attributes: "Replace/Create"
(the existing behavior), "Add", "Subtract", and "Multiply".
At this point, the operations are limited by what is simple to implement.
More could be added in the future, but there isn't a strong use case
for more complex operations anyway, and a second math node can be used.

Differential Revision: https://developer.blender.org/D10269