Add Aliyun OSS FileIO adapter

[manuzhang]

iceberg-cpp's FileIO registry currently has Arrow-local (src/iceberg/arrow/arrow_io_register.cc), Arrow-S3 (src/iceberg/arrow/s3/arrow_s3_file_io.cc), and REST-signed-URL (src/iceberg/catalog/rest/rest_file_io.cc). Aliyun OSS is missing.

Two reasonable implementations, either works:

1. Reuse Arrow's S3 client against an OSS endpoint (OSS speaks S3-compatible API for the most part). Plumbing-only; no new SDK dependency.
2. Wrap Aliyun OSS SDK directly. More features (e.g., STS token refresh, native multipart) but a heavier dep.

Path scheme to support: oss://<bucket>/<key>.

Properties to thread through: endpoint, region, access key id/secret, optional STS security token. Suggest mirroring src/iceberg/arrow/s3/s3_properties.h.

[manuzhang]

Upstream status: duplicate, foundation already in place.

• apache/iceberg-cpp#324 (OPEN) — "Are there any plans to support object storage?" — direct match.
• apache/iceberg-cpp#548 (MERGED) — feat: add s3 file io integration — provides the Arrow-S3 plumbing OSS would build on.

Recommendation: close this as duplicate. An OSS adapter is now a small follow-up to apache#548 (S3-compatible client pointed at OSS endpoint).