Add the Clip operator

Description

Add the support of the Clip operator.

New files : ClipImpl.hpp, ClipImpl.cpp, ClipImpl_forward_kernels.hpp, ClipImpl_backward_kernels.hpp

The Clip operator has been tested (forward and backward).

include/aidge/backend/cpu/operator/ClipImpl.hpp

+/********************************************************************************
+ * Copyright (c) 2023 CEA-List
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ ********************************************************************************/
+
+#ifndef AIDGE_CPU_OPERATOR_CLIPIMPL_H_
+#define AIDGE_CPU_OPERATOR_CLIPIMPL_H_
+
+#include <cstddef>  // std::size_t
+#include <memory>
+#include <tuple>    // std::tuple
+#include <vector>
+
+#include "aidge/backend/OperatorImpl.hpp"
+#include "aidge/operator/Clip.hpp"
+#include "aidge/utils/Registrar.hpp"
+#include "aidge/utils/Types.h"
+
+namespace Aidge {
+// class Clip_Op;
+
+// compute kernel registry for forward and backward
+class ClipImplForward_cpu
+    : public Registrable <ClipImplForward_cpu, 
+                          std::tuple<DataType, DataType>, 
+                          void(const float, const float, const std::size_t, const void*, void*)>{};
+
+class ClipImplBackward_cpu
+    : public Registrable <ClipImplBackward_cpu, 
+                          std::tuple<DataType, DataType, DataType>, 
+                          void(const float, const float, const std::size_t, const void*, const void*, void*)> {};
+
+class ClipImpl_cpu : public OperatorImpl {
+public:
+    ClipImpl_cpu(const Clip_Op& op) : OperatorImpl(op, "cpu") {}
+
+    static std::unique_ptr<ClipImpl_cpu> create(const Clip_Op& op) {
+        return std::make_unique<ClipImpl_cpu>(op);
+    }
+
+    Elts_t getNbRequiredProtected(const IOIndex_t inputIdx) const override final;
+
+    void forward() override final;
+
+    void backward() override final;
+};
+
+namespace {
+static Registrar<Clip_Op> registrarClipImpl_cpu("cpu", Aidge::ClipImpl_cpu::create);
+}
+}  // namespace Aidge
+
+#endif /* AIDGE_CPU_OPERATOR_CLIPIMPL_H_ */