[SPARK-11068] [SQL] [FOLLOW-UP] move execution listener to util

Author: Wenchen Fan <wenchen@databricks.com>

Closes #9119 from cloud-fan/callback.

sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala

@@ -45,6 +45,7 @@ import org.apache.spark.sql.execution.ui.{SQLListener, SQLTab}
 import org.apache.spark.sql.sources.BaseRelation
 import org.apache.spark.sql.types._
 import org.apache.spark.sql.{execution => sparkexecution}
+import org.apache.spark.sql.util.ExecutionListenerManager
 import org.apache.spark.util.Utils
 
 /**

sql/core/src/main/scala/org/apache/spark/sql/QueryExecutionListener.scala → sql/core/src/main/scala/org/apache/spark/sql/util/QueryExecutionListener.scala

@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-package org.apache.spark.sql
+package org.apache.spark.sql.util
 
 import java.util.concurrent.locks.ReentrantReadWriteLock
 import scala.collection.mutable.ListBuffer

sql/core/src/test/scala/org/apache/spark/sql/DataFrameCallbackSuite.scala → sql/core/src/test/scala/org/apache/spark/sql/util/DataFrameCallbackSuite.scala

@@ -15,9 +15,10 @@
  * limitations under the License.
  */
 
-package org.apache.spark.sql
+package org.apache.spark.sql.util
 
 import org.apache.spark.SparkException
+import org.apache.spark.sql.{functions, QueryTest}
 import org.apache.spark.sql.catalyst.plans.logical.{Aggregate, Project}
 import org.apache.spark.sql.execution.QueryExecution
 import org.apache.spark.sql.test.SharedSQLContext