[MINOR][BRANCH-2.4] Avoid hardcoded py4j-0.10.7-src.zip in Scala

## What changes were proposed in this pull request?

This PR targets to deduplicate hardcoded `py4j-0.10.7-src.zip` in order to make py4j upgrade easier.

## How was this patch tested?

N/A

Closes #24772 from HyukjinKwon/backport-minor-py4j.

Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
(cherry picked from commit 6715135)
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

core/src/main/scala/org/apache/spark/api/python/PythonUtils.scala

@@ -27,12 +27,15 @@ import org.apache.spark.SparkContext
 import org.apache.spark.api.java.{JavaRDD, JavaSparkContext}
 
 private[spark] object PythonUtils {
+  val PY4J_ZIP_NAME = "py4j-0.10.7-src.zip"
+
   /** Get the PYTHONPATH for PySpark, either from SPARK_HOME, if it is set, or from our JAR */
   def sparkPythonPath: String = {
     val pythonPath = new ArrayBuffer[String]
     for (sparkHome <- sys.env.get("SPARK_HOME")) {
       pythonPath += Seq(sparkHome, "python", "lib", "pyspark.zip").mkString(File.separator)
-      pythonPath += Seq(sparkHome, "python", "lib", "py4j-0.10.7-src.zip").mkString(File.separator)
+      pythonPath +=
+        Seq(sparkHome, "python", "lib", PY4J_ZIP_NAME).mkString(File.separator)
     }
     pythonPath ++= SparkContext.jarOfObject(this)
     pythonPath.mkString(File.pathSeparator)

resource-managers/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala

@@ -48,6 +48,7 @@ import org.apache.hadoop.yarn.exceptions.ApplicationNotFoundException
 import org.apache.hadoop.yarn.util.Records
 
 import org.apache.spark.{SecurityManager, SparkConf, SparkException}
+import org.apache.spark.api.python.PythonUtils
 import org.apache.spark.deploy.{SparkApplication, SparkHadoopUtil}
 import org.apache.spark.deploy.yarn.config._
 import org.apache.spark.deploy.yarn.security.YARNHadoopDelegationTokenManager
@@ -1182,7 +1183,7 @@ private[spark] class Client(
         val pyArchivesFile = new File(pyLibPath, "pyspark.zip")
         require(pyArchivesFile.exists(),
           s"$pyArchivesFile not found; cannot run pyspark application in YARN mode.")
-        val py4jFile = new File(pyLibPath, "py4j-0.10.7-src.zip")
+        val py4jFile = new File(pyLibPath, PythonUtils.PY4J_ZIP_NAME)
         require(py4jFile.exists(),
           s"$py4jFile not found; cannot run pyspark application in YARN mode.")
         Seq(pyArchivesFile.getAbsolutePath(), py4jFile.getAbsolutePath())

resource-managers/yarn/src/test/scala/org/apache/spark/deploy/yarn/YarnClusterSuite.scala

@@ -33,6 +33,7 @@ import org.scalatest.Matchers
 import org.scalatest.concurrent.Eventually._
 
 import org.apache.spark._
+import org.apache.spark.api.python.PythonUtils
 import org.apache.spark.deploy.SparkHadoopUtil
 import org.apache.spark.deploy.yarn.config._
 import org.apache.spark.internal.Logging
@@ -257,7 +258,7 @@ class YarnClusterSuite extends BaseYarnClusterSuite {
     // needed locations.
     val sparkHome = sys.props("spark.test.home")
     val pythonPath = Seq(
-        s"$sparkHome/python/lib/py4j-0.10.7-src.zip",
+        s"$sparkHome/python/lib/${PythonUtils.PY4J_ZIP_NAME}",
         s"$sparkHome/python")
     val extraEnvVars = Map(
       "PYSPARK_ARCHIVES_PATH" -> pythonPath.map("local:" + _).mkString(File.pathSeparator),