constraints_list of flat zonotopes is wrong

[schillic]

The constraints_list of zonotopes uses the cross_product function, which computes the determinant on a submatrix containing some generators. If the zonotope is flat in some dimension, all generators are zero in that dimension, which makes the determinant zero as well.

I think this is the cause of #3038.

Below is an example. It needs to be 3D because there is a check to use the V-representation (see the code snippet), which always triggers for flat 2D zonotopes.

LazySets.jl/src/Interfaces/AbstractZonotope.jl

Lines 510 to 519 in 65463d0

	use_vrep = (p < n) # order < 1
	if !use_vrep
	# remove redundant generators and check again
	Z = remove_redundant_generators(Z)
	p = ngens(Z)
	use_vrep = (p < n)
	end
	if use_vrep
	return _constraints_list_vrep(Z)
	end

julia> Z = Zonotope(zeros(3), [1.0 1 0; 0 1 1; 0 0 0]);

julia> constraints_list(Z)  # clearly wrong because the set should have proper bounds in dimensions 1 and 2
6-element Vector{LazySets.HalfSpace{Float64, Vector{Float64}}}:
 LazySets.HalfSpace{Float64, Vector{Float64}}([0.0, -0.0, 1.0], 0.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.0, 0.0, -1.0], 0.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([0.0, -0.0, 1.0], 0.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.0, 0.0, -1.0], 0.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([0.0, -0.0, 1.0], 0.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.0, 0.0, -1.0], 0.0)

julia> constraints_list(VPolytope(vertices_list(Z)))  # correct solution via V-representation
8-element Vector{LazySets.HalfSpace{Float64, Vector{Float64}}}:
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.0, -0.0, -1.0], 0.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([0.0, 0.0, 1.0], -0.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.0, -1.0, -0.0], 2.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.3333333333333333, -0.0, -0.0], 0.6666666666666666)
 LazySets.HalfSpace{Float64, Vector{Float64}}([0.5, -0.5, -0.0], 1.0)
 LazySets.HalfSpace{Float64, Vector{Float64}}([0.2, -0.0, -0.0], 0.4)
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.16666666666666666, 0.16666666666666666, -0.0], 0.3333333333333333)
 LazySets.HalfSpace{Float64, Vector{Float64}}([-0.0, 0.14285714285714288, -0.0], 0.28571428571428575)