Use `int64_t` for CAGRA+HNSW search function

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The CAGRA+HNSW search function is using uint64_t when all ANN search functions are using int64_t. It would be better to unify this API. Milvus created a fix for this on Raft : https://github.com/rapidsai/raft/commit/10f5414eaa895ee0d566fa2932eb102c518bfcb4