This PR updates to use cuVS instead of RAFT for vector search, pairwise distances and clustering. This is required for us to deprecate the vector search functionality in RAFT, in favour of the code in cuVS.

Because some code hasn't been migrated over to cuvs yet, we will continue to use the version in RAFT - but with RAFT in header only mode. In particular this functionality will be used in RAFT header only mode:

* Random Ball Cover (see rapidsai/cuvs#218)
* Sparse KNN
* nn-descent rapidsai/cuvs#364
* [MetricProcessor](c7d1b0e)
* knn_merge_parts
* build_dendrogram_host
* build_sorted_mst
*  raft DistanceType

Because sparse KNN in RAFT uses the DistanceType in RAFT, we can't fully move over to use the DistanceType code in cuVS with this PR. (Also the DistanceType code in RAFT has a `Precomputed` option that isn't available in cuvs - but is needed by cuml for dbscan.)  This means that we have both the raft and cuvs DistanceType enum's in use with this change, with conversions between them.

Authors:
  - Ben Frederickson (https://github.com/benfred)
  - Bradley Dice (https://github.com/bdice)
  - Kyle Edwards (https://github.com/KyleFromNVIDIA)
  - Corey J. Nolet (https://github.com/cjnolet)

Approvers:
  - Corey J. Nolet (https://github.com/cjnolet)
  - Dante Gama Dessavre (https://github.com/dantegd)
  - Bradley Dice (https://github.com/bdice)

URL: #6085