Logical type definition for parquet.variant in arrow-java

[tmater]

Describe the enhancement requested

Parquet has added a new type for semi-structured data called Variant which is defined here:

• Variant encoding spec: https://github.com/apache/parquet-format/blob/main/VariantEncoding.md
• Variant shredding spec: https://github.com/apache/parquet-format/blob/main/VariantShredding.md

This ticket intended to track the Logical type definition first.

Background

Discussion about accepting the format: apache/arrow#42069

The format has already been accepted: apache/arrow#46908

The format has already been implemented in for example C++: apache/arrow#45937