[SPARK-24811][FOLLOWUP][SQL] Revise package of AvroDataToCatalyst and CatalystDataToAvro

## What changes were proposed in this pull request?

In #21838, the class `AvroDataToCatalyst` and `CatalystDataToAvro` were put in package `org.apache.spark.sql`.
They should be moved to package  `org.apache.spark.sql.avro`.
Also optimize imports in Avro module.

## How was this patch tested?

Unit test

Closes #22196 from gengliangwang/avro_revise_package_name.

Authored-by: Gengliang Wang <[email protected]>
Signed-off-by: hyukjinkwon <[email protected]>

Author: gengliangwang

external/avro/src/main/scala/org/apache/spark/sql/avro/AvroDataToCatalyst.scala

@@ -15,13 +15,12 @@
  * limitations under the License.
  */
 
-package org.apache.spark.sql
+package org.apache.spark.sql.avro
 
 import org.apache.avro.Schema
 import org.apache.avro.generic.GenericDatumReader
 import org.apache.avro.io.{BinaryDecoder, DecoderFactory}
 
-import org.apache.spark.sql.avro.{AvroDeserializer, SchemaConverters}
 import org.apache.spark.sql.catalyst.expressions.{ExpectsInputTypes, Expression, UnaryExpression}
 import org.apache.spark.sql.catalyst.expressions.codegen.{CodegenContext, CodeGenerator, ExprCode}
 import org.apache.spark.sql.types.{AbstractDataType, BinaryType, DataType}

external/avro/src/main/scala/org/apache/spark/sql/avro/CatalystDataToAvro.scala

@@ -15,16 +15,15 @@
  * limitations under the License.
  */
 
-package org.apache.spark.sql
+package org.apache.spark.sql.avro
 
 import java.io.ByteArrayOutputStream
 
 import org.apache.avro.generic.GenericDatumWriter
 import org.apache.avro.io.{BinaryEncoder, EncoderFactory}
 
-import org.apache.spark.sql.avro.{AvroSerializer, SchemaConverters}
 import org.apache.spark.sql.catalyst.expressions.{Expression, UnaryExpression}
-import org.apache.spark.sql.catalyst.expressions.codegen.{CodegenContext, CodeGenerator, ExprCode}
+import org.apache.spark.sql.catalyst.expressions.codegen.{CodegenContext, ExprCode}
 import org.apache.spark.sql.types.{BinaryType, DataType}
 
 case class CatalystDataToAvro(child: Expression) extends UnaryExpression {

external/avro/src/test/scala/org/apache/spark/sql/avro/AvroCatalystDataConversionSuite.scala

@@ -17,15 +17,12 @@
 
 package org.apache.spark.sql.avro
 
-import org.apache.avro.Schema
-
 import org.apache.spark.SparkFunSuite
-import org.apache.spark.sql.{AvroDataToCatalyst, CatalystDataToAvro, RandomDataGenerator}
+import org.apache.spark.sql.RandomDataGenerator
 import org.apache.spark.sql.catalyst.{CatalystTypeConverters, InternalRow}
 import org.apache.spark.sql.catalyst.expressions.{ExpressionEvalHelper, GenericInternalRow, Literal}
 import org.apache.spark.sql.catalyst.util.{ArrayBasedMapData, GenericArrayData, MapData}
 import org.apache.spark.sql.types._
-import org.apache.spark.unsafe.types.UTF8String
 
 class AvroCatalystDataConversionSuite extends SparkFunSuite with ExpressionEvalHelper {