refactor: remove unused CometAesDecrypt direct path

AesDecrypt extends RuntimeReplaceable in Spark, so it is always
rewritten to StaticInvoke before Comet's serde runs. Remove the
direct CometAesDecrypt handler and CometAesDecryptHelper, keeping
only the CometAesDecryptStaticInvoke path.

Author: rafafrdz

spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala

@@ -222,7 +222,8 @@ object QueryPlanSerde extends Logging with CometExprShim {
 
   private val miscExpressions: Map[Class[_ <: Expression], CometExpressionSerde[_]] = Map(
     // TODO PromotePrecision
-    classOf[AesDecrypt] -> CometAesDecrypt,
+    // AesDecrypt extends RuntimeReplaceable and is rewritten to StaticInvoke before Comet's
+    // serde runs, so it is handled via CometStaticInvoke / CometAesDecryptStaticInvoke.
     classOf[Alias] -> CometAlias,
     classOf[AttributeReference] -> CometAttributeReference,
     classOf[BloomFilterMightContain] -> CometBloomFilterMightContain,

spark/src/main/scala/org/apache/comet/serde/misc.scala

@@ -19,15 +19,18 @@
 
 package org.apache.comet.serde
 
-import org.apache.spark.sql.catalyst.expressions.{AesDecrypt, Attribute, Expression}
+import org.apache.spark.sql.catalyst.expressions.Attribute
 import org.apache.spark.sql.catalyst.expressions.objects.StaticInvoke
 
 import org.apache.comet.serde.ExprOuterClass.Expr
 import org.apache.comet.serde.QueryPlanSerde.{exprToProtoInternal, optExprWithInfo, scalarFunctionExprToProtoWithReturnType}
 
-private object CometAesDecryptHelper {
-  def convertToAesDecryptExpr[T <: Expression](
-      expr: T,
+// AesDecrypt extends RuntimeReplaceable in Spark, so by the time Comet's serde runs it has
+// already been replaced with a StaticInvoke. This handler is registered in CometStaticInvoke's
+// staticInvokeExpressions map under the ("aesDecrypt", ExpressionImplUtils) key.
+object CometAesDecryptStaticInvoke extends CometExpressionSerde[StaticInvoke] {
+  override def convert(
+      expr: StaticInvoke,
       inputs: Seq[Attribute],
       binding: Boolean): Option[Expr] = {
     val childExpr = expr.children.map(exprToProtoInternal(_, inputs, binding))
@@ -39,21 +42,3 @@ private object CometAesDecryptHelper {
     optExprWithInfo(optExpr, expr, expr.children: _*)
   }
 }
-
-object CometAesDecrypt extends CometExpressionSerde[AesDecrypt] {
-  override def convert(
-      expr: AesDecrypt,
-      inputs: Seq[Attribute],
-      binding: Boolean): Option[Expr] = {
-    CometAesDecryptHelper.convertToAesDecryptExpr(expr, inputs, binding)
-  }
-}
-
-object CometAesDecryptStaticInvoke extends CometExpressionSerde[StaticInvoke] {
-  override def convert(
-      expr: StaticInvoke,
-      inputs: Seq[Attribute],
-      binding: Boolean): Option[Expr] = {
-    CometAesDecryptHelper.convertToAesDecryptExpr(expr, inputs, binding)
-  }
-}