[FEATURE REQUEST]: Spark 4.0 support for VariantType

**Is your feature request related to a problem? Please describe.**
Need to utilize the VariantType data type in Spark 4.0 to describe things like JsonObject in a schema.

**Describe the solution you'd like**
Add `VariantType` as a supported data type.

**Describe alternatives you've considered**
Making my own data type for the time being...

```csharp
public sealed class VariantType : DataType
{
}
```

**Additional context**
https://spark.apache.org/docs/latest/api/java//org/apache/spark/sql/types/DataTypes.html