Epic: Variant Type and Array

[AdamGS]

This Epic is for adding a variant type, inspired by Clickhouse's Variant and Dynamic types and Parquet/Spark's variant type.

It includes:

1. A new dtype
2. New canonical type
3. Support for zero-copy support for Arrow's new Parquet-Variant encoding.
4. A new VariantGet expression, used to pull data out variant arrays.

Status

Proposed.

Goal

Motivation

Unresolved questions

• None yet.