Generalize plotting to non-convex sets and add some functionality for VPolygonNC

[schillic]

There are no docstrings nor tests (to be added in #3124), but the functions are simple (they were just required for plotting) and I tried plotting manually.

[David-davidlxl]

The following code produces an incorrect plot of a nonconvex polygon:

using LazySets
using Plots

polygon = VPolygon([[0, 0],
    [2.1314, 0.9141],
    [1.8282, 1.2219],
    [0.9141, 0.9141],
    [0.6063, 1.5251],
    [-0.6063, 2.1360],
    ], apply_convex_hull=false)

plot(polygon)

Did I plot it incorrectly or is this a bug?

[schillic]

@David-davidlxl: The type was renamed to Polygon.

polygon = Polygon([[0, 0],
    [2.1314, 0.9141],
    [1.8282, 1.2219],
    [0.9141, 0.9141],
    [0.6063, 1.5251],
    [-0.6063, 2.1360]])