Correct member initialization order (#2254)

The init order of class members needs to follow the order listed in the class. This corrects the error for the cagra index type, as it was found to be wrong via rapidsai/cuvs#66

Authors:
  - Robert Maynard (https://github.com/robertmaynard)

Approvers:
  - Corey J. Nolet (https://github.com/cjnolet)

URL: #2254

cpp/include/raft/neighbors/cagra_types.hpp

@@ -205,8 +205,8 @@ struct index : ann::index {
         raft::distance::DistanceType metric = raft::distance::DistanceType::L2Expanded)
     : ann::index(),
       metric_(metric),
-      dataset_(new neighbors::empty_dataset<int64_t>(0)),
-      graph_(make_device_matrix<IdxT, int64_t>(res, 0, 0))
+      graph_(make_device_matrix<IdxT, int64_t>(res, 0, 0)),
+      dataset_(new neighbors::empty_dataset<int64_t>(0))
   {
   }
 
@@ -271,8 +271,8 @@ struct index : ann::index {
         mdspan<const IdxT, matrix_extent<int64_t>, row_major, graph_accessor> knn_graph)
     : ann::index(),
       metric_(metric),
-      dataset_(make_aligned_dataset(res, dataset, 16)),
-      graph_(make_device_matrix<IdxT, int64_t>(res, 0, 0))
+      graph_(make_device_matrix<IdxT, int64_t>(res, 0, 0)),
+      dataset_(make_aligned_dataset(res, dataset, 16))
   {
     RAFT_EXPECTS(dataset.extent(0) == knn_graph.extent(0),
                  "Dataset and knn_graph must have equal number of rows");