feat(parquet): add row number reader for selected row groups

[advancedxy]

What

Add a RowNumberReader, modeled after parquet-rs, that emits absolute file row positions from the selected Parquet row groups.

Use the resulting position array for _pos and inherited _row_id in record-batch projection. Preserve physical lineage values and cross-row-group batching. Restore consumed ranges if array construction fails so the batch can be retried.

Why

Follow-up to the row-position tracking discussion in #956.

Updating next_file_pos by the emitted batch size assumes contiguous file rows. Row-group pruning can introduce gaps, so each selected row must retain its original position in the file.

Testing

• parquet_test, arrow_test, and avro_test passed.
• Coverage includes skipped/reordered row groups, batches spanning row groups, physical and inherited lineage, and allocation-failure recovery.
• Pre-commit and git diff --check passed.

Limitations and follow-up

The Iceberg-side RowNumberReader can account for row-group-level skipping only: it knows the selected row groups and their row counts. It cannot account for page-level skipping inside Arrow C++ because the skipped row ranges are not exposed alongside the output batches; batch lengths alone are insufficient to recover the original positions.

Supporting page-level skipping requires integrating row-number generation into Arrow C++'s Parquet reader, where it can stay synchronized with page skipping and the actual rows emitted. This is the planned follow-up. Iceberg C++ can then consume that position array for _pos and inherited _row_id, replacing its local RowNumberReader. Keeping position generation separate from Iceberg metadata semantics prepares for that integration.

[advancedxy]

not satisfied about these nullptr changes yet, however I don't find a more elegant way to passing row positions as it will touch all the ProjectedXXXMethods.

happy to take suggestions.