Fix T98813: crash with GPU subdiv in edit mode and instanced geometry

Instancing with geometry nodes uses just the evaluated Mesh, and ignores the
Object that it came from. That meant that it would try to look up the subsurf
modifier on the instancer object which does not have the subsurf modifier.

Instead of storing a session UUID and looking up the modifier data, store a
point to the subsurf modifier runtime data. Unlike the modifier data, this
runtime data is preserved across depsgraph CoW. It must be for the subdiv
descriptor contained in it to stay valid along with the draw cache.

As a bonus, this moves various Mesh_Runtime variables into the subsurf runtime
data, reducing memory usage for meshes not using subdivision surfaces.

Also fixes T98693, issues with subdivision level >= 8 due to integer overflow.

Differential Revision: https://developer.blender.org/D15184

source/blender/draw/intern/draw_cache_impl_mesh.cc

@@ -2068,8 +2068,7 @@ void DRW_mesh_batch_cache_create_requested(struct TaskGraph *task_graph,
   }
 
   if (do_subdivision) {
-    DRW_create_subdivision(scene,
-                           ob,
+    DRW_create_subdivision(ob,
                            me,
                            cache,
                            &cache->final,