Release v0.0.21

- Update version to 0.0.21 in all components
- Python packages: hindsight-api, hindsight-dev, hindsight-dev/benchmarks, hindsight-all
- Python client: hindsight-clients/python
- TypeScript client: hindsight-clients/typescript
- Rust CLI: hindsight-cli
- Control Plane: hindsight-control-plane
- Helm chart