SOCI Index Manifest v2 support

[chlunde]

Would it be possible to reduce container startup time for images built with JIB by adding a SOCI (Seekable OCI) index?

Integrated support in JIB, if that is possible, would make it easier to use.

https://github.com/awslabs/soci-snapshotter/blob/main/docs/soci-index-manifest-v2.md