All C++ datatypes & components now implement a new Loggable trait (#4305

)

### What

This moves all serialization related methods off of the respective
structs themselves, leading to better auto complete.
`AsComponents`.
The default implementations of `AsComponents` now all require input
types to implement this new trait - before they just required the
to_data_cell method to be there (that's still the case, but now with an
indirection ;))

This makes our interface cleaner and paves the way to a good fix for:
* #3260

(there's a few details still missing for this to allow custom types
without dragging in arrow headers, but one thing at a time!)

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/4305) (if
applicable)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG

- [PR Build Summary](https://build.rerun.io/pr/4305)
- [Docs
preview](https://rerun.io/preview/c494b2e513d28ed53b456caaf890901bd2d7c6b4/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/c494b2e513d28ed53b456caaf890901bd2d7c6b4/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)