This adds a `Convert Curves to Legacy Hair` operator. It converts all selected curves objects into particle hair systems on their respective surface objects. Existing particle systems with the correct name are updated, otherwise new a new particle system is added.
The purpose of the operator is to make the new curves sculpting tools useful even before all functionality is ported over.
{F12953790}
Currently, the generated hair system does not map exactly to the curves object for reasons that I don't fully understand. It's very close though. It might be a drawing issue or the hair strands are resampled somewhere else.