Fix duplicate filtering path in Arrow task batches (#3448)

Closes #3272

## What this changes

This PR updates the Arrow scan path in `_task_to_record_batches` to
avoid redundant filtering when there are no positional deletes.

- Keeps predicate pushdown in `Scanner.from_fragment` as the only filter
path when `positional_deletes` is absent.
- Applies `current_batch.filter(pyarrow_filter)` only in the
positional-delete path, after deletes are applied.
- Preserves empty-batch handling after both delete application and
conditional filtering.

## Why

The previous flow could perform an extra table-level refilter even when
the scanner already applied the predicate. This change removes that
stale workaround path while keeping correct behavior for positional
delete scenarios.

## Tests

Added regression coverage in `tests/io/test_pyarrow.py`:

-
`test_task_to_record_batches_filter_without_positional_deletes_avoids_table_refilter`
-
`test_task_to_record_batches_filter_with_positional_deletes_handles_empty_batch`

Validated locally:

- `python -m pytest tests/io/test_pyarrow.py -q -k
"task_to_record_batches_nanos or
filter_without_positional_deletes_avoids_table_refilter or
filter_with_positional_deletes_handles_empty_batch"`
- `make lint`

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Co-authored-by: Gayathri Srividya Rajavarapu <gayathrir@Gayathris-MacBook-Air.local>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Fokko Driesprong <fokko@apache.org>