Use the BKE_gpencil_stroke_uniform_subdivide function to subdivide strokes
before interpolation. When the target/source stroke is smaller than the other
stroke, it is subdivided until the lengths match. This improves the overall quality
of the interpolation of different sized strokes.
Before/After video:
{F9511779}
Reviewed By: #grease_pencil, antoniov, pepeland, mendio
Differential Revision: https://developer.blender.org/D9839