[FEA] CAGRA vector addition - support large graph and dataset

[tfeher]

PR #2157 enables vector addition to a CAGRA index. Some issues that can come up with large datasets / graph:

• graph in host memory not supported by extend https://github.com/rapidsai/raft/pull/2157/files#r1561657193
• Can we allocate new dataset and graph with the same allocator that was used with the original index? https://github.com/rapidsai/raft/pull/2157/files#r1560675342