Start to Load World State

This patch starts to load world state for debugging. The next step is to make sure that deserialization exactly matches the format of world.takeSnapshot().

examples3d/all_examples3.rs

@@ -25,6 +25,7 @@ mod debug_friction3;
 mod debug_infinite_fall3;
 mod debug_prismatic3;
 mod debug_rollback3;
+mod debug_serialized3;
 mod debug_shape_modification3;
 mod debug_triangle3;
 mod debug_trimesh3;
@@ -122,6 +123,10 @@ pub fn main() {
             "(Debug) shape modification",
             debug_shape_modification3::init_world,
         ),
+        (
+            "A serialized",
+            debug_serialized3::init_world,
+        ),
     ];
 
     // Lexicographic sort, with stress tests moved at the end of the list.