Add Apache Iceberg backend

Describe the feature:
Apache Iceberg as storage and maybe search

Describe a specific use case for the feature:
Supporting Apache iceberg to store and search brings ACID for free and reduce infra structure requirements, because S3 or minio would be used behind the scene.

The issue names no files, tests, or entry points to inspect. First clarify whether Apache Iceberg should provide storage, search, or both, and define the supported S3 or MinIO use case and acceptance criteria before implementation can be started.

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