[lake/iceberg] Implement SupportsRecordBatchWrite for IcebergLakeWriter

### Search before asking

- [x] I searched in the [issues](https://github.com/apache/fluss/issues) and found nothing similar.

### Motivation

Paimon's lake writer implements `SupportsRecordBatchWrite` (landed in #3417/#3418), enabling direct Arrow batch to Parquet writes for append-only tables. This avoids the row-by-row serialization overhead through `GenericRecord` objects.

The Iceberg lake writer (`IcebergLakeWriter`) currently writes row-by-row via `GenericAppenderFactory`, resulting in significantly lower throughput for append-only log table tiering compared to the Paimon path.

Since Fluss uses Arrow as its internal columnar format, and both Iceberg and Parquet have native Arrow support (`iceberg-arrow` module, `parquet-arrow` module), we can bridge the Arrow batch directly to Iceberg Parquet files.

### Solution

1. Make `IcebergLakeWriter` implement `SupportsRecordBatchWrite`
2. Create an Arrow batch writer that takes `ArrowBatchData` and writes to Iceberg Parquet files
3. Only enabled for append-only tables (same restriction as Paimon)
4. Preserve Iceberg file metrics tracking for proper table maintenance

Related: #437 (generic arrow-to-parquet issue)

### Upstream Issues for True Zero-Copy Path

The current PR (#4048) implements `SupportsRecordBatchWrite` by reading Arrow vectors and producing `GenericRecord` objects. This avoids binary log deserialization but still materializes row objects because Iceberg and parquet-java lack columnar write APIs.

Upstream issues filed to enable true zero-copy Arrow-to-Parquet writes:

1. **[apache/parquet-java#3733](https://github.com/apache/parquet-java/issues/3733)** — Add `ParquetWriter` to the `parquet-arrow` module. This is the foundational primitive.
2. **[apache/iceberg#17748](https://github.com/apache/iceberg/issues/17748)** — Add `FileAppender` to Iceberg's arrow module. Depends on (or works alongside) the parquet-java change.

Once these land, Fluss can replace the `IcebergArrowBatchHelper` (GenericRecord bridge) with a direct call to Iceberg's vectorized appender.

### Anything else?

All necessary primitives exist in upstream Iceberg (`iceberg-arrow` 1.10.1) and Apache Parquet (`parquet-arrow`). No upstream changes needed for the initial implementation; upstream changes enable the optimized path.

### Willingness to contribute

- [x] I'm willing to submit a PR!

Start with IcebergLakeWriter and compare its GenericAppenderFactory path with the Paimon SupportsRecordBatchWrite implementation. Trace ArrowBatchData through IcebergArrowBatchHelper, then verify append-only restrictions and Iceberg file metrics; PR #4048 already describes an implementation to compare against.

Written by the indexing model from the issue text.