While calculating interpolated points, intervals between two baked
points has been assummed to be `baked_interval`. The assumption could
cause significant error in some extreme cases (for example #7088).
To improve accuracy, `baked_dist_cache` is introduced, which stores
distance from starting point for each baked points. `interpolate_baked`
now returns exact linear-interpolated position along baked points.
Jihyun Yu
8a6fc54ccd