[FEA] Use PQ public API in Vamana and SCANN

[lowener]

Vamana and SCANN make use of some PQ functions taken from the VPQ codebase.
Ideally they would use the public PQ API when ready to minimize binary size and have a single entry point for PQ-related code.
Depends on #1278

[tarang-jain]

Potentially related issue: #1182

[lowener]

As referenced in #1278 (comment) Vamana removes the VQ index so it should have use_vq=false in it's future params

[lowener]

Vamana switched to PQ public API in #1278