[Add] 'Producer_Op' tensor constructor now copies the backend of its output Tensor

include/aidge/operator/Producer.hpp

@@ -51,6 +51,8 @@ public:
         : OperatorTensor(Type, 0, 0, 1),
         Attributes_(attr<ProdAttr::Constant>(constant))
     {
+        if (tensor->getImpl())
+            mImpl = Registrar<Producer_Op>::create(tensor->getImpl()->backend())(*this);
         mOutputs[0] = tensor; // copy the pointer of the Tensor
     }