⚠️ (go/v4) decouple webhooks from APIs (Move Webhooks from api/<version> or api/<group>/<version> to internal/webhook/<version> or internal/webhook/<group>/<version>)

⚠️ (go/v4) decouple webhooks from APIs (Move Webhooks from api/<version> or api/<group>/<version> to internal/webhook/<version> or internal/webhook/<group>/<version>) #521