This is a change split from the geometry nodes curves branch. Since
curve object modifier evaluation happens in this file, moving it to C++
will be quite helpful to support the `GeometrySet` type. Other than
that, the code in the branch intends to replace a fair amount of this
file anyway, so I don't plan to do any further cleanup here.
Differential Revision: https://developer.blender.org/D11078
7e17dbfcf3