feat(linear_algebra/affine_space/basis): `reindex` API (#18190)
Rename and change arguments to `affine_basis.comp_equiv` so that it matches `basis.reindex`. Provide lemmas for its interaction with other `affine_basis` constructions.
Make `affine_basis` follow the `fun_like` design, replacing `affine_basis.points` by a function coercion.
Fix a few names all around:
* `affine_basis.coord_apply_neq` → `affine_basis.coord_apply_ne`
* `convex_hull_affine_basis_eq_nonneg_barycentric` → `affine_basis.convex_hull_eq_nonneg_coord`
