[Graphbolt] Pass down the original eid. (#6444)

Co-authored-by: Ubuntu <ubuntu@ip-172-31-28-63.ap-northeast-1.compute.internal>

python/dgl/graphbolt/impl/neighbor_sampler.py

@@ -124,6 +124,7 @@ class NeighborSampler(SubgraphSampler):
                 node_pairs=compacted_node_pairs,
                 original_column_node_ids=original_column_node_ids,
                 original_row_node_ids=seeds,
+                original_edge_ids=subgraph.original_edge_ids,
             )
             subgraphs.insert(0, subgraph)
         return seeds, subgraphs