MG KMeans initialization emits unnecessary warnings

[viclafargue]

The multi-GPU KMeans initialization and more specifically the reclustering step of the KMeans|| initialization method emits unnecessary/confusing warnings when used in MNMG mode (RAFT communicator).

This is caused by the fact that the reclustering step of the KMeans|| initialization method calls the public MG KMeans API interface that handles SG/MG dispatch.

The warning :

Multi-GPU handle detected on single-GPU kmeans::fit() entry; falling back to single-GPU. Use cuvs::cluster::kmeans::mg::fit(...) for multi-GPU.