folly::IOBuf does not have TreeBuilder v2 container support. Add it.
The implementation is a direct clone of v1. It still lacks tests.
Test Plan:
- It codegens on a prod type.
- No runtime testing... Bad form, I know.
- Issue created to add integration tests: https://github.com/facebookexperimental/object-introspection/issues/436
This change is fully backwards compatible with the old ContainerInfo
parser, as it is just adding new fields.
The old fields will continue to be used by legacy OICodeGen until that
is removed.
Also add a README to document the format.
