The node should be faster than in 3.1, for a few reasons:

• It doesn't need to calculate and allocate the curve offsets.
• It doesn't need to de-reference a pointer for each curve.
• The inputs are accessed from the virual arrays fewer times.

On top of that, I added two other performance improvements:

• The node is multi-threaded when there are many curves.
• There are generated special cases for single value and span inputs.

To make the code a bit simpler, I added new methods to IndexRange
to mirror what is available for Span.

Performance
With a set position node affecting 1 million splines with a selection
based on this node, on an Intel i5 8250U (times are approximate):

This will also include the performance increase for the set position node
from 4c66bd5da256779ef5a308d86a.