Polyhedron.affine_hull: New option 'unimodular'

[mkoeppe]

We add a new option unimodular, which will be useful for lattice point applications.

More generally, given a (not necessarily orthogonal) direct sum decomposition of the ambient space into a rational vector space L #30203 and a direct complement M, use an affine transformation that is lattice-preserving for L and, depending on the other options, arbitrary/orthogonal/orthonormal for M.

Depends on #27366

CC: @kliem

Component: geometry

Issue created by migration from https://trac.sagemath.org/ticket/31730