V3 Tracking issue

Tracks the progress of the V3 implementation

- [ ] New DataTypes
- [x] **UnknownType**: Added in https://github.com/apache/iceberg-python/pull/1681
- [x] **Timestamp(Tz)NanoType**: Introduced in https://github.com/apache/iceberg-python/pull/1632
- [ ] **VariantType**: https://github.com/apache/iceberg-python/issues/1819
- [ ] **Geometry**/**Geography**: https://github.com/apache/iceberg-python/issues/1820
- [ ] Default value:
- [x] https://github.com/apache/iceberg-python/issues/1836 / https://github.com/apache/iceberg-python/pull/1644
- [x] https://github.com/apache/iceberg-python/pull/1770
- [x] Prerequisite: https://github.com/apache/iceberg-python/pull/1805
- [x] Multi-arg transforms
- Reading of the metadata has been added in https://github.com/apache/iceberg-python/pull/1554
- Supporting multi-arg transforms still needs to happen
- [x] Row-level lineage
- https://github.com/apache/iceberg-python/issues/1821
- [ ] Deletion vectors
- [x] Read support is being added in https://github.com/apache/iceberg-python/pull/1516
- [ ] Write support

Beginne damit, die verknüpften V3-Unterthemen und Pull Requests zu VariantType, Geometry/Geography, row-level lineage, multi-argument transforms und deletion-vector write support zu prüfen. Das Tracking-Issue ist erst abgeschlossen, wenn jedes nicht abgehakte V3-Checklistenelement erledigt und die damit verknüpfte Arbeit abgeschlossen ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.