[SPARK-3858][SQL] Pass the generator alias into logical plan node

The alias parameter is being ignored, which makes it more difficult to specify a qualifier for Generator expressions.

Author: Nathan Howell <nhowell@godaddy.com>

Closes #2721 from NathanHowell/SPARK-3858 and squashes the following commits:

8aa0f43 [Nathan Howell] [SPARK-3858][SQL] Pass the generator alias into logical plan node

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

@@ -360,7 +360,7 @@ class SchemaRDD(
       join: Boolean = false,
       outer: Boolean = false,
       alias: Option[String] = None) =
-    new SchemaRDD(sqlContext, Generate(generator, join, outer, None, logicalPlan))
+    new SchemaRDD(sqlContext, Generate(generator, join, outer, alias, logicalPlan))
 
   /**
    * Returns this RDD as a SchemaRDD.  Intended primarily to force the invocation of the implicit

sql/core/src/test/scala/org/apache/spark/sql/DslQuerySuite.scala

@@ -147,6 +147,14 @@ class DslQuerySuite extends QueryTest {
       (1, 1, 1, 2) :: Nil)
   }
 
+  test("SPARK-3858 generator qualifiers are discarded") {
+    checkAnswer(
+      arrayData.as('ad)
+        .generate(Explode("data" :: Nil, 'data), alias = Some("ex"))
+        .select("ex.data".attr),
+      Seq(1, 2, 3, 2, 3, 4).map(Seq(_)))
+  }
+
   test("average") {
     checkAnswer(
       testData2.groupBy()(avg('a)),