[FEA] Support SCaNN in `cuvs-bench`

[cjnolet]

cuvs-bench tool is important for several reasons. For one, it allows us to provide reprocible benchmarks that users can run on their own hardware. Another reason is that we often run these benchmarks to verify there are no performance regressions in between releases, and when perf regressions are found, it allows us to profile and debug.

We've recently added Vamana/DiskANN indexes to cuvs-bench, both for GPU and for the CPU reference, which was also needed to evaluate searching the Vamana indexes we've built on the GPU. We should do the same with SCaNN.