Add "for_write" on function names that retrieve mutable data arrays.
Though this makes function names longer, it's likely worth it because
it allows more easily using the const functions in a non-const context,
and reduces cases of mistakenly retrieving with edit access.
In the long term, this situation might change more if we implement
attributes storage that is accessible directly on `CurvesGeometry`
without duplicating the attribute API on geometry components,
which is currently the rough plan.
Differential Revision: https://developer.blender.org/D14562
8551e89068