This node sets the selected (or all) splines in curve to a chosen target
spline type. Poly, Bezier, and NURB splines can be converted to any of
the other types. This is meant to be a building block node, useful in
many procedural situations.
In the future the node could be optimized with multi-threading, or by
avoiding copying in many cases, either by retrieving the curve for write
access or by passing the raw vectors to the new splines where possible.
With edits from Hans Goudey (@HooglyBoogly)
Differential Revision: https://developer.blender.org/D12013