move to bi-directional streaming for source, map, transformer, and sink for better performance

[vigith]

Summary

The integration between numa and SDK server should be via gRPC Streaming and not unary for better performance. We should even move half-duplex to bi-di.

Use Cases

Getting Numaflow ready for future performance improvements.

### Tasks
- [ ] https://github.com/numaproj/numaflow/issues/2045
- [ ] Add Stop and Stopped to Source gRPC (no-op)
- [ ] https://github.com/numaproj/numaflow/issues/2046
- [ ] https://github.com/numaproj/numaflow/issues/2092
- [ ] https://github.com/numaproj/numaflow/issues/2091

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