Geometry Nodes: Attribute Vector Math Node

This patch implements the same operations and interface as the regular
vector math node, but it runs for every element of the attribute. This
should expand what's possible with geometry nodes quite a bit.

Differential Revision: https://developer.blender.org/D9914

release/scripts/startup/nodeitems_builtins.py

@@ -488,6 +488,7 @@ geometry_node_categories = [
         NodeItem("GeometryNodeAttributeFill"),
         NodeItem("GeometryNodeAttributeMix"),
         NodeItem("GeometryNodeAttributeColorRamp"),
+        NodeItem("GeometryNodeAttributeVectorMath"),
     ]),
     GeometryNodeCategory("GEO_COLOR", "Color", items=[
         NodeItem("ShaderNodeValToRGB"),