Fix broken Handedness test

MeshImporter was always changing handedness regardless of the importOptions.

Cameras were not sanitized so I added a new SanitizedCameraSample

Author: judubu

package/com.unity.formats.usd/Runtime/Scripts/IO/SanitizedSamples.cs

@@ -29,6 +29,18 @@ public void Sanitize(Scene scene, SceneImportOptions importOptions)
         }
     }
 
+    /// <summary>
+    /// A sanitizable version of an CameraSample. Enable automatic change of handedness.
+    /// </summary>
+    public class SanitizedCameraSample : CameraSample, ISanitizable
+    {
+        public void Sanitize(Scene scene, SceneImportOptions importOptions)
+        {
+            if (importOptions.changeHandedness != BasisTransformation.FastWithNegativeScale)
+                ConvertTransform();
+        }
+    }
+
     /// <summary>
     /// A sanitizable version of a MeshSample. Enable automatic triangulation/handedness change/attribute interpolation conversion.
     /// </summary>
@@ -69,14 +81,15 @@ public class SanitizedMeshSample : MeshSample, ISanitizable
         /// </summary>
         public void Sanitize(Scene scene, SceneImportOptions importOptions)
         {
+            var changeHandedness = importOptions.changeHandedness == BasisTransformation.SlowAndSafe ||
+                importOptions.changeHandedness == BasisTransformation.SlowAndSafeAsFBX;
             // Start with the xform
-            if (importOptions.changeHandedness != BasisTransformation.FastWithNegativeScale)
+            if (changeHandedness)
                 ConvertTransform();
 
             var santizePrimvars = importOptions.ShouldBindMaterials ||
                 scene.IsPopulatingAccessMask || scene.AccessMask != null;                        //this is true when reading from the timeline
 
-            var changeHandedness = true;
             var unwindVertices = ShouldUnwindVertices(changeHandedness);
             if (points == null)
                 return;

package/com.unity.formats.usd/Runtime/Scripts/IO/Scene/SceneImporter.cs

@@ -711,11 +711,12 @@ public static IEnumerator BuildScene(Scene scene,
             if (importOptions.importCameras)
             {
                 Profiler.BeginSample("USD: Cameras");
-                foreach (var pathAndSample in scene.ReadAll<CameraSample>(primMap.Cameras))
+                foreach (var pathAndSample in scene.ReadAll<SanitizedCameraSample>(primMap.Cameras))
                 {
                     try
                     {
                         GameObject go = primMap[pathAndSample.path];
+                        pathAndSample.sample.Sanitize(scene, importOptions);
                         NativeImporter.ImportObject(scene, go, scene.GetPrimAtPath(pathAndSample.path), importOptions);
                         XformImporter.BuildXform(pathAndSample.path, pathAndSample.sample, go, importOptions, scene);