Summary:
Add ability to search HNSW indexes using a plain [`SearchParameters`](https://github.com/facebookresearch/faiss/blob/6c046992a71e672df504a0101cddf6f2f2e90601/faiss/Index.h#L64-L69) object (i.e. only an [`IDSelector`](https://github.com/facebookresearch/faiss/blob/6c046992a71e672df504a0101cddf6f2f2e90601/faiss/Index.h#L66))

Issue: Currently if a plain `SearchParameters` is used to query an HNSW index, [an error is thrown](https://github.com/facebookresearch/faiss/blob/6c046992a71e672df504a0101cddf6f2f2e90601/faiss/IndexHNSW.cpp#L251) -- when the user's intent was only to filter some documents, and rely on index settings for remaining parameters (like `efSearch`, `check_relative_distance`, `search_bounded_queue`)

Motivation: Faiss provides an amazing [index factory](https://github.com/facebookresearch/faiss/wiki/The-index-factory) and [parameter setter](https://github.com/facebookresearch/faiss/wiki/Index-IO,-cloning-and-hyper-parameter-tuning) to abstract away internals of the index type and settings used, like:
```cpp
Index* index = index_factory(256, "HNSW32");
ParameterSpace().set_index_parameters(index, "efConstruction=200,efSearch=150");
```

Now if a user wants to perform a filtered search on this _opaque_ index using:
```cpp
SearchParameters parameters;
parameters.sel = new IDSelectorRange(10, 20);
index->search(nq, xq, k, d, id, &parameters);
```

they are met with an error:
```
faiss/IndexHNSW.cpp:251: Error: '!(params)' failed: params type invalid
```

An easy way to reproduce this issue is to replace `Flat` -> `HNSW` [here](https://github.com/facebookresearch/faiss/blob/6c046992a71e672df504a0101cddf6f2f2e90601/c_api/example_c.c#L60) and run `example_c` like:
```
make -C build example_c
./build/c_api/example_c
```

This PR allows passing a plain `SearchParameters` to HNSW indexes, and use index settings as a fallback


Reviewed By: asadoughi

Differential Revision: D69266072

Pulled By: mnorris11