By versioning the `dora-message` crate individually, we can use the
semver rules to encode which versions are compatible. This way, we can
allow different versions of dora to work together (e.g. CLI version can
be different than node API version), as long as the message formats are
compatible. Breaking message format changes are signaled by a
semver-incompatible release of `dora-message`. For example, 0.4.0 is not
compatible with 0.3.5.

One alternative approach could be to use the main version to signal
compatibility, i.e. the common version that we use for all dora crates.
This has the disadvantage that we might need to bump the minor version
of the main dora crate every time we want to change the message format
in a breaking way. As we still expect semi-regular breaking changes to
the message format in the near future, we want to avoid this churn. Once
we consider the message format more stable, we plan to revisit this
approach.

Fixes https://github.com/dora-rs/dora/issues/504

TODO

- [x] Update release script: We should not try to publish the
`dora-message` crate if there is no new version.
- [x] Relax version checks to only compare major/minor version
(according to semver compatibility rules).

First step towards versioning the message definitions indepedently.

Delay dropping of `DoraNode` in Python until all event data is freed

When dropping the `DoraNode`, it waits for the remaining drop tokens. This only works if all the dora events were already dropped before. With the Python GC, this is not guaranteed as some events might still be live on the heap (the user might even use them later). In such cases, we waited until we ran into a timeout, which resulted in very long exit times (see https://github.com/dora-rs/dora/issues/598).

This commit fixes this issue by adding a reference-counted copy of the `DoraNode` and `EventStream` to every event given to Python. This way, we can ensure that the underlying `DoraNode` is only dropped after the last event reference has been freed.

This remove the complexity of having to rename the node id when used within a yaml configuration.

Send runs artefacts into a dedicated `out` folder

Ensures that all raw data has at least an alignment of 128.

Empty `Vec`s have a dummy pointer that is set to the alignment of the item type. Thus, the pointer for empty `Vec<u8>` data is `0x1`. Using this pointer to construct a `ArrayData` instance can lead to alignment errors if the arrow array is of a type with larger alignment, e.g. float64.

This commit fixes the alignment error by checking for an empty raw buffer and constructing an empty `ArrayData` instance in this case.

Fixes #362

- If input has no data, return an empty `NullArray` instead of an empty byte array.
- If input contains Vec data (instead of shared memory data), use safe `arrow::buffer::Buffer::from_vec` constructor, which is also zero-copy.

Makes the distinction between raw data and data messages clearer.

- introduce a new `ArrayData` wrapper struct
- implement `TryFrom` to convert to primitive types and strings
- update examples to use the new conversion functions

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.