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

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.

test new crates version release

test rc 2 version

fix version typo

Test crates.io new dora tag release

Removing those path make it easier to move package, reduce path management
reduce complexity and make it easier to export crates to `crates.io`

The intent of this commit is to remove the quantity of log that is being pushed to user.

This commit removes the redeclaration of a set up tracing methods to centralise
the tokio-tracing subscriber within the extension crate. It also add the
feature to filter information based on Environment variable.
This makes it possible to define the log level for tokio tracing like
this:
```
RUST_LOG=debug dora-daemon --run-dataflow dataflow.yml
```

I have also unified the feature flag to make it easier to manage tracing features among the workspace.

I did not change the default behaviour of tracing in our crates and therefore by
using the command above you should get the same tracing log as before.

fix merge conflict generated

To prepare for future feature, this commit initiate a `__init__.py` file
that makes the dora python node api, a mixed python/rust project.

Any python function or variable included in the `__init__.py` will be
distributed along rust function declared in `src/lib.rs`.

https://github.com/dora-rs/dora/issues/163 has shown the limitation on
depending too much on `pyo3`.

Co-authored-by: Haixuan Xavier Tao <tao.xavier@outlook.com>