geometry: mechanism for chamfered corners

[brandondube]

at the moment, all rasterized shapes have sharp corners. For nonconvex shapes (and even for convex shapes), this is not very manufacturable and prysm has no mechanism for rasterizing more manufacturable shapes, per-se. Bezier curves are one way to accomplish this, which has the benefit of being compatible with the vertex-based approach used by the convex polygon shader. Others would include figuring out how to do the bitwise masking on offset circles, but there is a bit of trickiness there.

[brandondube]

this was implemented sometime in the last year for rectangles with rounded corners. The same logic can be used to make "bowties" with rounded corners as needed in the future