[SPARK-11983][SQL] remove all unused codegen fallback trait

Author: Daoyuan Wang <daoyuan.wang@intel.com>

Closes #9966 from adrian-wang/removeFallback.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala

@@ -104,8 +104,7 @@ object Cast {
 }
 
 /** Cast the child expression to the target data type. */
-case class Cast(child: Expression, dataType: DataType)
-  extends UnaryExpression with CodegenFallback {
+case class Cast(child: Expression, dataType: DataType) extends UnaryExpression {
 
   override def toString: String = s"cast($child as ${dataType.simpleString})"
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala

@@ -66,7 +66,7 @@ trait StringRegexExpression extends ImplicitCastInputTypes {
  * Simple RegEx pattern matching function
  */
 case class Like(left: Expression, right: Expression)
-  extends BinaryExpression with StringRegexExpression with CodegenFallback {
+  extends BinaryExpression with StringRegexExpression {
 
   override def escape(v: String): String = StringUtils.escapeLikeRegex(v)
 
@@ -117,7 +117,7 @@ case class Like(left: Expression, right: Expression)
 
 
 case class RLike(left: Expression, right: Expression)
-  extends BinaryExpression with StringRegexExpression with CodegenFallback {
+  extends BinaryExpression with StringRegexExpression {
 
   override def escape(v: String): String = v
   override def matches(regex: Pattern, str: String): Boolean = regex.matcher(str).find(0)

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/NonFoldableLiteral.scala

@@ -26,8 +26,7 @@ import org.apache.spark.sql.types._
  * A literal value that is not foldable. Used in expression codegen testing to test code path
  * that behave differently based on foldable values.
  */
-case class NonFoldableLiteral(value: Any, dataType: DataType)
-  extends LeafExpression with CodegenFallback {
+case class NonFoldableLiteral(value: Any, dataType: DataType) extends LeafExpression {
 
   override def foldable: Boolean = false
   override def nullable: Boolean = true