Add an offset argument in the tensor copy function

include/aidge/backend/TensorImpl.hpp

@@ -21,7 +21,7 @@ class TensorImpl {
 public:
     TensorImpl() = delete;
     TensorImpl(const char *backend) : mBackend(backend){};
-    virtual void copy(const void *src, NbElts_t length) = 0;
+    virtual void copy(const void *src, NbElts_t length, std::size_t offset = 0) = 0;
     virtual void *rawPtr() = 0;
     virtual void setRawPtr(void* /*ptr*/)
     {