Javadoc
Finds the largest contiguous area of "on" cells in this GreasedRegion and returns it; does not modify this
GreasedRegion. If there are multiple areas that are all equally large with no larger area, this returns the
region it checks first and still is largest (first determined by the same ordering
#nth(int) takes).
This may return an empty GreasedRegion if there are no "on" cells, but it will never return null.
Here, contiguous means adjacent on an orthogonal direction, and this doesn't consider diagonally-connected cells
as contiguous unless they also have an orthogonal connection.