[SPARK-21767][TEST][SQL] Add Decimal Test For Avro in VersionSuite

## What changes were proposed in this pull request?
Decimal is a logical type of AVRO. We need to ensure the support of Hive's AVRO serde works well in Spark

## How was this patch tested?
N/A

Author: gatorsmile <gatorsmile@gmail.com>

Closes #18977 from gatorsmile/addAvroTest.