Refactor PhysX vehicles and cloth simulation code to be more readable

#2796

Source/Engine/Physics/Actors/Cloth.cpp

@@ -27,6 +27,11 @@ Cloth::Cloth(const SpawnParams& params)
     _drawCategory = SceneRendering::SceneDrawAsync;
 }
 
+void* Cloth::GetPhysicsCloth() const
+{
+    return _cloth;
+}
+
 ModelInstanceActor::MeshReference Cloth::GetMesh() const
 {
     auto value = _mesh;

Source/Engine/Physics/Actors/Cloth.h

@@ -13,7 +13,6 @@
 /// </summary>
 API_CLASS(Attributes="ActorContextMenu(\"New/Physics/Cloth\"), ActorToolbox(\"Physics\")") class FLAXENGINE_API Cloth : public Actor
 {
-    friend class PhysicsBackend;
     DECLARE_SCENE_OBJECT(Cloth);
 
     /// <summary>
@@ -231,6 +230,11 @@ private:
     Array<float> _paint;
 
 public:
+    /// <summary>
+    /// Gets the native physics backend object.
+    /// </summary>
+    void* GetPhysicsCloth() const;
+
     /// <summary>
     /// Gets the mesh to use for the cloth simulation (single mesh from specific LOD). Always from the parent static or animated model actor.
     /// </summary>

Source/Engine/Physics/Actors/WheeledVehicle.h

@@ -13,6 +13,7 @@
 API_CLASS(Attributes="ActorContextMenu(\"New/Physics/Wheeled Vehicle\"), ActorToolbox(\"Physics\")") class FLAXENGINE_API WheeledVehicle : public RigidBody
 {
     friend class PhysicsBackend;
+    friend struct ScenePhysX;
     DECLARE_SCENE_OBJECT(WheeledVehicle);
 
     /// <summary>