Internal function to calculate 2D convex hull coordinates and area. This function replaces the dependency on SIBER::siberConvexhull.
convexhull(x, y)A list containing:
Total area of the convex hull
x-coordinates of hull vertices
y-coordinates of hull vertices
x-coordinates of hull vertices (alternative name for compatibility)
y-coordinates of hull vertices (alternative name for compatibility)
Row names of points on the hull
numeric vector of x-coordinates
numeric vector of y-coordinates