…okincubator#16870)

Summary:

Add deletion vector (DV) reader to the Velox Iceberg connector,
enabling Iceberg V3 spec support for row-level deletes.

Iceberg V3 replaces positional delete files with deletion vectors — compact
roaring bitmaps stored as blobs inside Puffin files. Compared to V2 positional
delete files, DVs are more compact and avoid sorted merge of multiple delete
files at read time.

Changes:
- IcebergDeleteFile.h: Add FileContent::kDeletionVector enum value
- DeletionVectorReader.h/cpp: New reader that loads a Puffin blob,
  deserializes the roaring bitmap portable format (array, bitset, and run
  containers), and sets bits in the deleteBitmap for the current batch range.
  No CRoaring dependency — self-contained parser.
- IcebergSplitReader.h: Add deletionVectorReaders_ member, include header
- IcebergSplitReader.cpp: Route kDeletionVector in prepareSplit(), apply
  DVs alongside positional deletes in next()
- BUCK: Add DeletionVectorReader library target

Differential Revision: D97530142

…ookincubator#16871)

Summary:

Implements Iceberg equality delete support for the Velox Iceberg connector.

Equality delete files contain rows with values for one or more columns
(identified by equalityFieldIds). A base data row is deleted if its values
match ALL specified columns of ANY row in the delete file.

The implementation:
- Adds EqualityDeleteFileReader that eagerly reads the entire delete file
  and builds an in-memory hash multimap of delete key tuples during
  construction.
- Wires EqualityDeleteFileReader into IcebergSplitReader::prepareSplit()
  to resolve equalityFieldIds to column names/types from the table schema,
  and into IcebergSplitReader::next() to apply post-read equality delete
  filtering with row compaction.
- Handles lazy vectors from file readers via loadedVector() before
  accessing values for hashing and comparison.
- Supports BOOLEAN, TINYINT, SMALLINT, INTEGER, BIGINT, REAL, DOUBLE,
  VARCHAR, VARBINARY, and TIMESTAMP column types.

Differential Revision: D97530141

…ality deletes (facebookincubator#16872)

Summary:

Implements Iceberg V2+ sequence number conflict resolution for equality
delete files. Per the Iceberg spec, an equality delete file should only
be applied to data files whose data sequence number is strictly less
than the delete file's data sequence number. This prevents concurrent
write conflicts where a delete file written concurrently with a data
file could incorrectly delete rows that were not intended to be deleted.

Changes:
- Added `dataSequenceNumber` field to `IcebergDeleteFile` struct with
  default value 0 (unassigned/legacy V1). When 0, sequence number
  filtering is disabled for backward compatibility.
- Added `dataSequenceNumber` field to `HiveIcebergSplit` to carry the
  base data file's sequence number.
- Updated `IcebergSplitReader::prepareSplit()` to skip equality delete
  files when `deleteFile.dataSequenceNumber <= split.dataSequenceNumber`
  (unless either is 0, which disables the check).
- Updated test constructor of `HiveIcebergSplit` to accept the new
  `dataSequenceNumber` parameter.

Differential Revision: D97530136