sagemathgh-39496: Add deformation cones and checking for regularity for Point Configurations and normal fans of Polyhedra
    
In this pull request, we add the method `deformation_cone` (to point
configurations and polyhedron) and `is_polytopal` (to fans).

This is related to the Kahler cone of Toric Varieties, but has some
subtle differences to make it work as it should in the discrete geometry
context. Therefore, it has a separate implementation.

TODO: In the future, perhaps it could be fusioned.

```sage
sage: tc = Polyhedron([(1, -1), (1/3, 1), (1, 1/3), (-1, 1), (-1, -1)])
sage: dc = tc.deformation_cone()
sage: dc.an_element()
(2, 1, 1, 0, 0)
sage: [_.A() for _ in tc.Hrepresentation()]
[(1, 0), (0, 1), (0, -1), (-3, -3), (-1, 0)]
sage: P = Polyhedron(rays=[(1, 0, 2), (0, 1, 1), (0, -1, 1), (-3, -3,
0), (-1, 0, 0)])
sage: P.rays()
(A ray in the direction (-1, -1, 0),
 A ray in the direction (-1, 0, 0),
 A ray in the direction (0, -1, 1),
 A ray in the direction (0, 1, 1),
 A ray in the direction (1, 0, 2))

sage: py = Polyhedron([(0, -1, -1), (0, -1, 1), (0, 1, -1), (0, 1, 1),
(1, 0, 0)])
sage: dc_py = py.deformation_cone(); dc_py
A 4-dimensional polyhedron in QQ^5 defined as the convex hull of 1
vertex, 1 ray, 3 lines
sage: [ineq.b() for ineq in py.Hrepresentation()]
[0, 1, 1, 1, 1]
sage: r = dc_py.rays()[0]
sage: l1,l2,l3 = dc_py.lines()
sage: r.vector()-l1.vector()/2-l2.vector()-l3.vector()/2
(0, 1, 1, 1, 1)
```

### 📝 Checklist

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preview.
    
URL: sagemath#39496
Reported by: JP Labbe
Reviewer(s): Frédéric Chapoton