This commit replaces the temporary conversion to `CurveEval` with
use of the new curves data-block. The end result is that the
process looks more like the other components-- somewhere in between
meshes and point clouds in terms of complexity.
The final result is that the logic between meshes and curves is
very similar. There are a few different strategies to reduce
duplication here, so I'll investigate that separately.
There is some special behavior for the radius and handle position
attributes. I used the attribute API to store spans of these
attributes temporarily. Using access methods on `CurvesGeometry`
would be reasonable to, storing spans separately feels a bit more
predictable for now though.
There should be significant performance improvements in some cases,
I haven't tested that specifically though.
Differential Revision: https://developer.blender.org/D14247
6c6f591f90