### What

* depends on #2937
* part of #2919 
* fixes #2791

Roundtrip test is part of #2937
Does not yet work in viewer because of
#2871

C++ extensions now get additional includes copied into the generated
header

Extensions circle around making use of the `Transform3D` archetype easy.
Note that the willingness of a c++ compiler to convert arrays and floats
to bool causes us quite a lot of extra overloads (luckily the added unit
tests catches these and there are warnings emitted).
The amount of overloads introduced leaves a bit of a bad taste, but the
expectation is that this is rather special to `Transform3D`. Some of the
provided overloads may be generated in the future if a pattern emerges.

A bunch of code example added to demonstrate what it looks like now to
use Transform3D:
```cpp
// translation only
rr_stream.log("translated", rr::artchetypes::Transform3D({1.0f, 0.0f, 0.0f}));

// translation/rotation/uniform-scale
rr_stream.log(
    "rotated_scaled",
    rr::archetypes::Transform3D(
        rrd::RotationAxisAngle({0.0f, 0.0f, 1.0f}, rrd::Angle::radians(pi / 4.0f)),
        2.0f
    )
);

// 3x3 matrix
rec_stream.log(
    "translation_and_mat3x3/rotation",
    rr::archetypes::Transform3D({
        {1.0f, 4.0f, 7.0f},
        {2.0f, 5.0f, 8.0f},
        {3.0f, 6.0f, 9.0f},
    })
);
```

### 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/2940) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/2940)
- [Docs
preview](https://rerun.io/preview/pr%3Aandreas%2Fcpp%2Ftransform3d/docs)
- [Examples
preview](https://rerun.io/preview/pr%3Aandreas%2Fcpp%2Ftransform3d/examples)