Update 'Operator::setOutput()' and overrides to be const

include/aidge/operator/Operator.hpp

@@ -109,7 +109,7 @@ public:
      * The pointer itself is not changed, thus keeping the current connections.
      * @param inputIdx Index of the input to set.
      */
-    virtual void setOutput(const IOIndex_t outputIdx, const std::shared_ptr<Data>& data) = 0;
+    virtual void setOutput(const IOIndex_t outputIdx, const std::shared_ptr<Data>& data) const = 0;
     virtual std::shared_ptr<Data> getRawOutput(const IOIndex_t outputIdx) const = 0;
 
     std::shared_ptr<Hook> getHook(const std::string& hookName) {

include/aidge/operator/OperatorTensor.hpp

@@ -62,7 +62,7 @@ public:
     std::shared_ptr<Data> getRawInput(const IOIndex_t inputIdx) const override final;
 
     // output management
-    void setOutput(const IOIndex_t outputIdx, const std::shared_ptr<Data>& data) override;
+    void setOutput(const IOIndex_t outputIdx, const std::shared_ptr<Data>& data) const override;
     virtual const std::shared_ptr<Tensor>& getOutput(const IOIndex_t outputIdx) const;
     std::shared_ptr<Aidge::Data> getRawOutput(const Aidge::IOIndex_t outputIdx) const override final;
     ///////////////////////////////////////////////////

include/aidge/operator/Producer.hpp

@@ -115,7 +115,7 @@ public:
         // fmt::print("Basic Producer backward() function.\n");
     }
 
-    void setOutput(const Aidge::IOIndex_t outputIdx, const std::shared_ptr<Aidge::Data>& data) override {
+    void setOutput(const Aidge::IOIndex_t outputIdx, const std::shared_ptr<Aidge::Data>& data) const override {
         if (mAttributes->template getAttr<ProdAttr::Constant>()) {
             AIDGE_THROW_OR_ABORT(std::runtime_error, "Producer is constant, cannot update output.");
         }

src/operator/OperatorTensor.cpp

@@ -73,7 +73,7 @@ const std::shared_ptr<Aidge::Tensor>& Aidge::OperatorTensor::getInput(const Aidg
     return mInputs[inputIdx];
 }
 
-void Aidge::OperatorTensor::setOutput(const Aidge::IOIndex_t outputIdx, const std::shared_ptr<Aidge::Data>& data) {
+void Aidge::OperatorTensor::setOutput(const Aidge::IOIndex_t outputIdx, const std::shared_ptr<Aidge::Data>& data) const {
     AIDGE_ASSERT(data->type() == Tensor::Type, "{} Operator only accepts Tensors as inputs", type());
     AIDGE_ASSERT(outputIdx < nbOutputs(), "{} Operator has {} outputs", type(), nbOutputs());
     const auto& data_tensor = std::dynamic_pointer_cast<Tensor>(data);