[SPARK-50905][SQL][TESTS] Rename Customer* to Custom* in `SparkSe…

…ssionExtensionSuite`

### What changes were proposed in this pull request?

This PR aims to rename `Customer*` to `Custom*` in `SparkSessionExtensionSuite` like the other existing ones in the same file.
- `CustomAggHint`
- `CustomAggregateRule`
- `CustomSortHint`
- `CustomSortRule`

### Why are the changes needed?

To make the comment and code consistently by using a general term `Custom` instead of `Customer`.

### Does this PR introduce _any_ user-facing change?

No, this is a renaming in test cases.

### How was this patch tested?

Pass the CIs.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#49587 from dongjoon-hyun/SPARK-50905.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

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

@@ -549,7 +549,7 @@ class SparkSessionExtensionSuite extends SparkFunSuite with SQLHelper with Adapt
   test("custom aggregate hint") {
     // The custom hint allows us to replace the aggregate (without grouping keys) with just
     // Literal.
-    withSession(Seq(_.injectHintResolutionRule(CustomerAggregateHintResolutionRule),
+    withSession(Seq(_.injectHintResolutionRule(CustomAggregateHintResolutionRule),
       _.injectOptimizerRule(CustomAggregateRule))) { session =>
       val res = session.range(10).agg(max("id")).as("max_id")
         .hint("MAX_VALUE", "id", 10)
@@ -562,7 +562,7 @@ class SparkSessionExtensionSuite extends SparkFunSuite with SQLHelper with Adapt
 
   test("custom sort hint") {
     // The custom hint allows us to replace the sort with its input
-    withSession(Seq(_.injectHintResolutionRule(CustomerSortHintResolutionRule),
+    withSession(Seq(_.injectHintResolutionRule(CustomSortHintResolutionRule),
       _.injectOptimizerRule(CustomSortRule))) { session =>
       val res = session.range(10).sort("id")
         .hint("INPUT_SORTED")
@@ -1263,7 +1263,7 @@ case class CustomAggHint(attribute: AttributeReference, max: Int) extends Aggreg
 
 // Attaches the CustomAggHint to the aggregate node without grouping keys if the aggregate
 // function is MAX over the specified column.
-case class CustomerAggregateHintResolutionRule(spark: SparkSession) extends Rule[LogicalPlan] {
+case class CustomAggregateHintResolutionRule(spark: SparkSession) extends Rule[LogicalPlan] {
   val MY_HINT_NAME = Set("MAX_VALUE")
 
   def isMax(expr: NamedExpression, attribute: String): Option[AttributeReference] = {
@@ -1316,7 +1316,7 @@ case class CustomAggregateRule(spark: SparkSession) extends Rule[LogicalPlan] {
 case class CustomSortHint(inputSorted: Boolean) extends SortHint
 
 // Attaches the CustomSortHint to the sort node.
-case class CustomerSortHintResolutionRule(spark: SparkSession) extends Rule[LogicalPlan] {
+case class CustomSortHintResolutionRule(spark: SparkSession) extends Rule[LogicalPlan] {
   val MY_HINT_NAME = Set("INPUT_SORTED")
 
   private def applySortHint(plan: LogicalPlan): LogicalPlan = plan.transformDown {