[Graphbolt] Move headers to include/graphbolt & add include guard (#5706)

graphbolt/include/csc_sampling_graph.h → graphbolt/include/graphbolt/csc_sampling_graph.h

 /**
  *  Copyright (c) 2023 by Contributors
- * @file graphbolt/include/csc_sampling_graph.h
+ * @file graphbolt/csc_sampling_graph.h
  * @brief Header file of csc sampling graph.
  */
+#ifndef GRAPHBOLT_CSC_SAMPLING_GRAPH_H_
+#define GRAPHBOLT_CSC_SAMPLING_GRAPH_H_
 
 #include <torch/custom_class.h>
 #include <torch/torch.h>
@@ -230,3 +232,4 @@ inline serialize::OutputArchive& operator<<(
     const graphbolt::sampling::CSCSamplingGraph& graph);
 
 }  // namespace torch
+#endif  //  GRAPHBOLT_CSC_SAMPLING_GRAPH_H_

graphbolt/include/serialize.h → graphbolt/include/graphbolt/serialize.h

 /**
  *  Copyright (c) 2023 by Contributors
- * @file graphbolt/include/serialize.h
+ * @file graphbolt/serialize.h
  * @brief Utility functions for serialize and deserialize.
  */
 
-#ifndef GRAPHBOLT_INCLUDE_SERIALIZE_H_
-#define GRAPHBOLT_INCLUDE_SERIALIZE_H_
+#ifndef GRAPHBOLT_SERIALIZE_H_
+#define GRAPHBOLT_SERIALIZE_H_
 
 #include <torch/torch.h>
 
@@ -142,4 +142,4 @@ void read_from_archive<std::vector<std::string>>(
 }  // namespace utils
 }  // namespace graphbolt
 
-#endif  // GRAPHBOLT_INCLUDE_SERIALIZE_H_
+#endif  // GRAPHBOLT_SERIALIZE_H_

graphbolt/src/csc_sampling_graph.cc

 /**
  *  Copyright (c) 2023 by Contributors
- * @file graphbolt/include/csc_sampling_graph.cc
+ * @file csc_sampling_graph.cc
  * @brief Source file of sampling graph.
  */
 
-#include "csc_sampling_graph.h"
-
-#include "serialize.h"
+#include <graphbolt/csc_sampling_graph.h>
+#include <graphbolt/serialize.h>
 
 namespace graphbolt {
 namespace sampling {