Introduce metadata for encrypting table data files

Question

Introduces the APIs and changes to schemas to support encryption in Iceberg table data files in the near future.

该提问来源于开源项目：apache/iceberg

Answer 1

This version mirrors most of what's in this design document. While building the code itself and thinking forward to how we'd actually generate the cryptographic streams with hadoop-crypto, I realized some minor discrepancies between what's in the document (at the time of commenting) and what's here. I'll indicate the changes in the PR and then shortly follow up with changes in the design document.

Overall this represents the major spirit of what's in the design document. It adds a notion of an opaque encryption key pointer, and a key manager API that can convert these pointers into structures from which we should be able to generate key materials and cryptographic streams.