Implement Variable-size List Layout

Implement read and write of the [Variable-size List Layout](https://arrow.apache.org/docs/format/Columnar.html#variable-size-list-layout) and verify against integration tests.

Start with the linked Apache Arrow Variable-size List Layout specification and inspect the existing read and write layout implementations in the repository. Then run the integration tests to understand their expected representation and verification. Done means Variable-size List Layout values can be read and written successfully and the integration tests pass.

Written by the indexing model from the issue text.