This adds a `geometry::smooth_curve_positions` function that
smoothes both bézier curves and all the other curve types.
Bézier curves are smoothed by joining the handle and control
points into a flat array, then using the 1D gaussian algorithm
and writing the resulting positions back into the left and right
handle positions as well as the control points. In general,
this works reasonably well and is similar to the results of the
other curve types.
Pull Request: https://projects.blender.org/blender/blender/pulls/125496
3a43493d85