feat: support dropping schema fields

[xxhZs]

Summary

• cherry-pick schema field drop support onto the release-2.8 iceberg-rust baseline
• keep the dependency line compatible with RisingWave release-2.8 instead of moving to the newer Arrow/Parquet stack

Testing

• consumed by iceberg-compaction and RisingWave release-2.8 checks

[xxhZs]

Closed because the target patch was corrected to fc28b1f; superseded by #159.