Move method in `IntegerLattice` to apply more generally

[user202729]

Currently, only ℤ-modules with a distinguished basis get methods like LLL or approximate_closest_vector or volume.

matrix([1, 2, 3]).right_kernel().volume()  # error (this should work!)
IntegerLattice(matrix([1, 2, 3]).right_kernel_matrix()).volume()  # works
#IntegerLattice(matrix([1, 2, 3]).right_kernel())  # loops forever

These methods in fact does not require a distinguished basis, as they are independent of the basis chosen. They could be moved upstream (to work with any ℤ-module, this may need creation of a new class).

[whoami730]

Can matrix_integer_dense or FreeModule_submodule_with_basis_integer be not used?

[user202729]

I don't think it's a good idea to make .right_kernel() return a ModuleWithBasis or a matrix. (currently it returns a module.)