Support Unity 6.7 content directory analysis (ContentLayout.json v3)

The schema of ContentLayout.json is changing between Unity 6.6 and 6.7 which breaks the ability to fully analyze content directory builds generated by Unity 6.7.

We need to update the support and try to maintain support for Unity 6.6 builds (the v2 schema). One approach might be to translate v2 to v3 files, and then only have support for importing the v3 data structures, this should be technically feasible because the changes only remove and reorganize data, no new data is added.

As part of this work https://github.com/Unity-Technologies/UnityDataTools/blob/main/Documentation/contentlayout.md should be reviewed to make sure it is accurate for both 6.6 and 6.7.

Inizia esaminando il percorso esistente di importazione e analisi di ContentLayout.json, confrontando gli schemi di Unity 6.6 v2 e 6.7 v3 descritti nell’issue. Esamina quindi Documentation/contentlayout.md per verificarne l’accuratezza in entrambe le versioni; il lavoro è completo quando le build della directory dei contenuti di 6.7 sono completamente analizzabili, mantenendo il supporto per le build di 6.6 v2.