resource control: use RUv2 consumption for RUv2 keyspaces

## Development Task

Resource control already tracks the RU version policy per keyspace and TiDB reports statement-level RUv2 consumption back to the PD client. However, the client-side token bucket still uses v1 RU (`RRU + WRU`) for token deduction and request judgement.

When a keyspace is configured to use RUv2, resource control should use RUv2 consumption for token accounting so throttling follows the active RU model.