fix GpuCreateNamedStruct not serializable issue

sql-plugin/src/main/scala/com/nvidia/spark/rapids/GpuExpressions.scala

@@ -89,6 +89,18 @@ object GpuExpressionsUtils extends Arm {
    */
   def columnarEvalToColumn(expr: Expression, batch: ColumnarBatch): GpuColumnVector =
     resolveColumnVector(expr.columnarEval(batch), batch.numRows, expr.dataType)
+
+  /**
+   * Extract the GpuLiteral
+   * @param exp the input expression to be extracted
+   * @return an optional GpuLiteral
+   */
+  @scala.annotation.tailrec
+  def extractGpuLit(exp: Expression): Option[GpuLiteral] = exp match {
+    case gl: GpuLiteral => Some(gl)
+    case ga: GpuAlias => extractGpuLit(ga.child)
+    case _ => None
+  }
 }
 
 /**

sql-plugin/src/main/scala/org/apache/spark/sql/rapids/complexTypeCreator.scala

@@ -87,8 +87,16 @@ case class GpuCreateNamedStruct(children: Seq[Expression]) extends GpuExpression
     case Seq(name, value) => (name, value)
   }.toList.unzip
 
+  // Names will be serialized before Spark scheduling, and the returned type GpuScalar
+  // from GpuLiteral.columnarEval(null) can't be serializable, which causes
+  // `org.apache.spark.SparkException: Task not serializable` issue.
+  //
+  // And on the other hand, the calling for columnarEval(null) in the driver side is
+  // dangerous for GpuExpressions, we'll have to pull it apart manually.
   private lazy val names = nameExprs.map {
-    case g: GpuExpression => g.columnarEval(null)
+    case ge: GpuExpression =>
+      GpuExpressionsUtils.extractGpuLit(ge).map(_.value)
+        .getOrElse(throw new IllegalStateException(s"Unexpected GPU expression $ge"))
     case e => e.eval(EmptyRow)
   }