Implement Tensor::zeros()

Implement Tensor::zeros().

include/aidge/backend/opencv/data/TensorImpl.hpp

@@ -86,6 +86,10 @@ public:
 
     inline std::size_t scalarSize() const noexcept override final { return sizeof(T); }
 
+    void zeros() override final {
+        mData.setTo(cv::Scalar::all(T(0)));
+    }
+
     void copy(const void *src, NbElts_t length, NbElts_t offset = 0) override final {
         const T* srcT = static_cast<const T *>(src);
         T* dstT = static_cast<T *>(rawPtr(offset));