feat: improve observability

[uri-99]

On this first improvement of observability we aim to add OBS on:

• Batcher

  • [ ] Received Proofs -> Counter
  • [ ] Qty of proofs on queue -> Gauge
  • [ ] Created Tasks -> Counter
  • [ ] Last Batch Size -> Gauge
  • [ ] Open connections -> Gauge

• Aggregator

  • [x] Task responses -> Counter
  • [ ] Received Tasks -> Counter

[PatStiles]

Open telemetry has a rust sdk https://github.com/open-telemetry/opentelemetry-rust. It directly integrates into the tokio's tracing_suscriber crate. Here is a tutorial integrating it with jaeger https://tokio.rs/tokio/topics/tracing-next-steps. There is also an example here: https://github.com/open-telemetry/opentelemetry-rust/tree/main/examples/tracing-jaeger.