Matching data of multiple files in Examples

### Problem statement
Matching data across multiple files produced by the IO writers in `Examples` is not straightforward. As an example, with v44.0.0 (d5d65c794d3676034f37d89e555c131b5b7ad807), an update of the particle barcode has been integrated with #4600. Before v44.0.0, the particle barcodes were represented as a single number (`particle_id`) in the files. While it has been kept as a single number in `Examples/Io/Root/src/RootParticleWriter.cpp` with a hash, this single number became a vector in most of the other files hence making the matching harder than with a single key. In particular, the writing of `particleIds` in `Examples/Io/Root/src/RootTrackStatesWriter.cpp` seems to not work anymore and not even appearing as a key in the .root file.
In other files, like `spacepoints.root` and `measurement-simhit-map.csv` IDs of external objects are used to refer to those but those particular IDs are not found in the corresponding files (`measurement_id` not in `measurements.root` and `hit_id` not in `hits.csv`) while, for what I understood, those IDs correspond to the row number when reading the file, hence not explicit.

As adding IDs to every file might increase the file size, I can understand that a discussion is needed. However I think ensuring that data can be matched efficiently between different files ensure that all information can be retrieved and could be added as an integration test.