test: add unit tests for new utility functions

Add comprehensive unit tests for refactoring utilities:

- TensorHelpersTest: Test toSpan<T> for Tensor and EValue conversions
  * Float and int32 tensors
  * Multidimensional tensors
  * Empty tensors
  * Type safety and const correctness

- ComputerVisionProcessingTest: Test extractDetectionData
  * Single and multiple detections
  * Various indices and label formats
  * Edge cases (negative coords, fractional values)

- FrameTransformTest: Test inverseRotateBboxes batch helper
  * Batch rotation of multiple detections
  * Empty containers and single detection
  * Preservation of non-bbox fields

Updated CMakeLists.txt to register new test executables.

Author: benITo47

packages/react-native-executorch/common/rnexecutorch/tests/CMakeLists.txt

@@ -171,6 +171,13 @@ add_rn_test(FrameTransformTests unit/FrameTransformTest.cpp
     LIBS opencv_deps
 )
 
+add_rn_test(TensorHelpersTest unit/TensorHelpersTest.cpp)
+
+add_rn_test(ComputerVisionProcessingTest unit/ComputerVisionProcessingTest.cpp
+    SOURCES
+        ${RNEXECUTORCH_DIR}/utils/computer_vision/Processing.cpp
+)
+
 add_rn_test(BaseModelTests integration/BaseModelTest.cpp)
 
 add_rn_test(VisionModelTests integration/VisionModelTest.cpp