P3t3: add all_cell_handles() and all_cell_handles()

Periodic_3_triangulation_3/include/CGAL/Periodic_3_triangulation_3.h

@@ -1745,6 +1745,11 @@ public:
     return _tds.cells_end();
   }
 
+  auto all_cell_handles() const
+  {
+    return _tds.cell_handles();
+  }
+
   All_vertices_iterator all_vertices_begin() const {
     return _tds.vertices_begin();
   }
@@ -1752,6 +1757,11 @@ public:
     return _tds.vertices_end();
   }
 
+  auto all_vertex_handles() const
+  {
+    return _tds.vertex_handles();
+  }
+
   All_edges_iterator all_edges_begin() const {
     return _tds.edges_begin();
   }