Rounded corner detection for `LayerRefinementSpec`

[yuanshen-flexcompute]

This is a feature request for automatic detection rounded corners for LayerRefinementSpec. As an example, consider the below:

Currently, the corners of the metal (red) are not detected because they are slightly rounded. One common situation where this can occur is if the geometry is externally created, i.e. imported from GDS or STL.

In this situation, it would be helpful for the grid to snap to the 90 degree straight edges of the rounded corner. We could define some sort of detection cutoff using a bevel/chamfer-based parameter.

[yuanshen-flexcompute]

Here's one way it could work: