Fix spawning actors in viewport to have better origin placement

Empty Actor is a building block of hierarchies so don't include dummy bounds there.
Wait for dragged asset to be loaded for proper bounds.
Use mesh bounds for non-active Animated Model for accurate placement.

Source/Engine/Level/Actors/EmptyActor.cpp

@@ -7,16 +7,6 @@ EmptyActor::EmptyActor(const SpawnParams& params)
 {
 }
 
-#if USE_EDITOR
-
-BoundingBox EmptyActor::GetEditorBoundingBox() const
-{
-    const Vector3 size(50);
-    return BoundingBox(_transform.Translation - size, _transform.Translation + size);
-}
-
-#endif
-
 void EmptyActor::OnTransformChanged()
 {
     // Base