[SPARK-55572][SQL][TESTS] Upgrade MySQL image to 9.6.0

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

This PR aims to upgrade `MySQL` image to `9.6.0` for Apache Spark 4.2.0.

### Why are the changes needed?

To maintain our JDBC test coverage up-to-date by testing against the latest version of `MySQL`.
- https://dev.mysql.com/doc/relnotes/mysql/9.6/en/ (2026-01-20)

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

No.

### How was this patch tested?

Pass the CIs.

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

Generated-by: `Gemini 3 Pro (High)` on `Antigravity`

Closes #54346 from dongjoon-hyun/SPARK-55572.

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

Author: dongjoon-hyun

connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/MySQLDatabaseOnDocker.scala

@@ -18,7 +18,7 @@
 package org.apache.spark.sql.jdbc
 
 class MySQLDatabaseOnDocker extends DatabaseOnDocker {
-  override val imageName = sys.env.getOrElse("MYSQL_DOCKER_IMAGE_NAME", "mysql:9.2.0")
+  override val imageName = sys.env.getOrElse("MYSQL_DOCKER_IMAGE_NAME", "mysql:9.6.0")
   override val env = Map(
     "MYSQL_ROOT_PASSWORD" -> "rootpass"
   )

connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/MySQLIntegrationSuite.scala

@@ -31,9 +31,9 @@ import org.apache.spark.sql.types.ShortType
 import org.apache.spark.tags.DockerTest
 
 /**
- * To run this test suite for a specific version (e.g., mysql:9.2.0):
+ * To run this test suite for a specific version (e.g., mysql:9.6.0):
  * {{{
- *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.2.0
+ *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.6.0
  *     ./build/sbt -Pdocker-integration-tests
  *     "docker-integration-tests/testOnly org.apache.spark.sql.jdbc.MySQLIntegrationSuite"
  * }}}
@@ -364,9 +364,9 @@ class MySQLIntegrationSuite extends SharedJDBCIntegrationSuite {
 
 
 /**
- * To run this test suite for a specific version (e.g., mysql:9.2.0):
+ * To run this test suite for a specific version (e.g., mysql:9.6.0):
  * {{{
- *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.2.0
+ *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.6.0
  *     ./build/sbt -Pdocker-integration-tests
  *     "docker-integration-tests/testOnly *MySQLOverMariaConnectorIntegrationSuite"
  * }}}

connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/v2/MySQLIntegrationSuite.scala

@@ -27,9 +27,9 @@ import org.apache.spark.sql.types._
 import org.apache.spark.tags.DockerTest
 
 /**
- * To run this test suite for a specific version (e.g., mysql:9.2.0):
+ * To run this test suite for a specific version (e.g., mysql:9.6.0):
  * {{{
- *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.2.0
+ *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.6.0
  *     ./build/sbt -Pdocker-integration-tests "testOnly *v2*MySQLIntegrationSuite"
  * }}}
  */
@@ -316,9 +316,9 @@ class MySQLIntegrationSuite extends DockerJDBCIntegrationV2Suite with V2JDBCTest
 }
 
 /**
- * To run this test suite for a specific version (e.g., mysql:9.2.0):
+ * To run this test suite for a specific version (e.g., mysql:9.6.0):
  * {{{
- *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.2.0
+ *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.6.0
  *     ./build/sbt -Pdocker-integration-tests
  *     "docker-integration-tests/testOnly *MySQLOverMariaConnectorIntegrationSuite"
  * }}}

connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/v2/MySQLNamespaceSuite.scala

@@ -28,9 +28,9 @@ import org.apache.spark.sql.util.CaseInsensitiveStringMap
 import org.apache.spark.tags.DockerTest
 
 /**
- * To run this test suite for a specific version (e.g., mysql:9.2.0):
+ * To run this test suite for a specific version (e.g., mysql:9.6.0):
  * {{{
- *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.2.0
+ *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.6.0
  *     ./build/sbt -Pdocker-integration-tests "testOnly *v2*MySQLNamespaceSuite"
  * }}}
  */

connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/v2/join/MySQLJoinPushdownIntegrationSuite.scala

@@ -25,9 +25,9 @@ import org.apache.spark.sql.jdbc.v2.JDBCV2JoinPushdownIntegrationSuiteBase
 import org.apache.spark.tags.DockerTest
 
 /**
- * To run this test suite for a specific version (e.g., mysql:9.2.0):
+ * To run this test suite for a specific version (e.g., mysql:9.6.0):
  * {{{
- *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.2.0
+ *   ENABLE_DOCKER_INTEGRATION_TESTS=1 MYSQL_DOCKER_IMAGE_NAME=mysql:9.6.0
  *     ./build/sbt -Pdocker-integration-tests "testOnly *v2*MySQLIntegrationSuite"
  * }}}
  */