The only difference betwenn the two traits is the additional Send bound. We should unify this again using the trait-level impl trait feature once it's stable.

Previous implementation of the runtime would link `libpython` even though it
might not be required.

This commit put pyo3 dependency under a feature flag that is only active if
the runtime is called from python for a python operator.

This fix:
- https://github.com/dora-rs/dora/actions/runs/4879188973/jobs/8705515472
- https://github.com/dora-rs/dora/issues/280#issuecomment-1534058207
- and https://github.com/dora-rs/dora-drives/issues/58#event-9162532660

Instead of doing an additional copy to send them from the operator thread to the runtime thread.

This commit uses the new `allocate_data_sample` and `send_output_sample` methods introduced in d7cd370.

This is mostly about convenience when working with arrow data types, as the data is still being copied once.

We only support `UInt8` arrays right now.

Reuse same event type as for Python node API.

Sending bytes using arrow is possible through new `send_output_arrow` method.

Some applications might not need the data in arrow format. By creating a custom object, we can provide the data both as a classical `PyBytes` and as a zero-copy arrow array.

See #224 for details.

Don't bind the lifetime of the event to the `next` call anymore. This makes it possible to use the original event in Python, which does not support borrowed data or lifetimes. The drawback is that we no longer have the guarantee that an event is freed before the next call to `recv`.

Bump version to `v0.2.2-rc-2`

This commit adds the ability to use the `opentelemetry` feature flag at
runtime by using the env variable `DORA_TELEMETRY`. Using environment
variable reduce the need to do some argument drilling between our
different process as well as making configurable in the YAML at no cost.

Usage:

```bash
docker run -d -p6831:6831/udp -p6832:6832/udp -p16686:16686 jaegertracing/all-in-one:latest
DORA_TELEMETRY=true dora-daemon --run-dataflow dataflow.yml
```

Current limitation:

- The telemetry currently only work with Jaeger on the local network with
default port: 6831 and 6832.