MLECO-2874: Move NMS out of the OD use_case

* Add ImageUtils
* Move image related code from UseCaseCommonUtils to ImageUtils
* Move NMS related code to ImageUtils
* Delete test specific ImageUtils and use new ImageUtils

Signed-off-by: Richard Burton <richard.burton@arm.com>
Change-Id: Icbf5dd9c6a941b0126ecdf69a0c9d9969f22729f
diff --git a/tests/use_case/object_detection/InferenceTestYoloFastest.cc b/tests/use_case/object_detection/InferenceTestYoloFastest.cc
index d9cabbd..b3bd408 100644
--- a/tests/use_case/object_detection/InferenceTestYoloFastest.cc
+++ b/tests/use_case/object_detection/InferenceTestYoloFastest.cc
@@ -66,10 +66,10 @@
     const size_t copySz = inputTensor->bytes < IMAGE_DATA_SIZE ?
                             inputTensor->bytes : IMAGE_DATA_SIZE;
 
-    image::RgbToGrayscale(imageData,inputTensor->data.uint8,copySz);
+    arm::app::image::RgbToGrayscale(imageData,inputTensor->data.uint8,copySz);
 
     if(model.IsDataSigned()){
-        convertImgIoInt8(inputTensor->data.data, copySz);
+        arm::app::image::ConvertImgToInt8(inputTensor->data.data, copySz);
     }
 
     return model.RunInference();