* chore: move ns api from querier to router
* chore: add explanatory comment in querier about moved namespace API
* fix: add namespace service to router
* fix: querier returns unimplemented error for ns retention, not panic
* chore: reuse namespace -> proto in router ns api
* chore: grpc namespace - consume ns to avoid clone
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>