Update hnswlib to v0.8.0

[cocoa-xu]

This PR updated hnswlib to v0.8.0, and added the following functions:

• HNSWLib.BFIndex.get_max_elements/1
• HNSWLib.BFIndex.get_current_count/1
• HNSWLib.BFIndex.{set_num_threads/2,get_num_threads/1}
• HNSWLib.Index.index_file_size/1

[cocoa-xu]

Restarted Windows CI as it seems stuck for more than half an hour... Not sure about the reason...

[josevalim]

Yeah, Windows is still getting stuck for some reason. :(

[cocoa-xu]

Yeah, Windows is still getting stuck for some reason. :(

Yeah... I'll cancel the workflow and try it with latest version of Erlang and Elixir. If it still stuck, I'll try it on a physical machine or later.

[cocoa-xu]

Finally I have access to a physical Windows machine. It seems that the problem only occurs when testing HNSWLib.BFIndex.delete_vector/2, i.e., mix test test/hnswlib_bfindex_test.exs:315

C:\Users\cocoa\Documents\GitHub\hnswlib>mix test test/hnswlib_index_test.exs
................................................
Finished in 2.3 seconds (0.00s async, 2.3s sync)
48 tests, 0 failures

Randomized with seed 921679

C:\Users\cocoa\Documents\GitHub\hnswlib>mix test test/hnswlib_bfindex_test.exs:315
# crashed