Enhance visibility of BezierCurve and NURBSCurve discretization functions

[kennyweiss]

Our C2CReader class has functionality to discretize a NURBSCurve class into linear segments, either into a user-supplied number of uniform segments per knot interval, or to approximate the curve within a user-specified error tolerance. The result is returned as an unstructured mint mesh of linear segments.

We should move this functionality to quest::Discretize.{hc}pp (https://github.com/LLNL/axom/blob/develop/src/axom/quest/Discretize.hpp) and to return the result as an array of primal::Segment to better match the quest::discretize interface.

This would enable any NURBSCurve user (and perhaps also BezierCurve users) to discretize their curves, rather than just while reading in C2C contours.