Complete deletion vector feature support #916

Goal

Complete end-to-end Iceberg v3 deletion vector support, building on #637 and #777.

Roadmap

• DV-PR-1 — feat: add table-aware position delete updates #919: Delete rows by file and position, merge existing deletes, and atomically commit v3 Puffin DVs while preserving v2 Parquet behavior.
• DV-PR-2 — fix: support all non-negative int64 deletion vector positions #917: Store sparse delete positions through INT64_MAX without allocating intervening bitmap buckets; preserve the wire format.
• DV-PR-3 — feat: add position_deletes metadata table #920: Expose Parquet position deletes and Puffin DVs through the position_deletes metadata table, including stored rows and partition metadata.
• DV-PR-4 — feat: add deletion vector compaction planning and execution #921: Plan and execute compaction within partition/spec boundaries, apply deletes, and atomically replace data files and obsolete delete entries. Depends on feat: add table-aware position delete updates #919.