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

Start by reviewing the linked V3 sub-issues and pull requests for VariantType, Geometry/Geography, row-level lineage, multi-argument transforms, and deletion-vector write support. The tracking issue is done only when every unchecked V3 checklist item has been completed and its linked work is resolved.

Written by the indexing model from the issue text.