[SPARK-27563][SQL][TEST] automatically get the latest Spark versions in HiveExternalCatalogVersionsSuite

## What changes were proposed in this pull request?

We can get the latest downloadable Spark versions from https://dist.apache.org/repos/dist/release/spark/

## How was this patch tested?

manually.

Closes #24454 from cloud-fan/test.

Authored-by: Wenchen Fan <wenchen@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

Author: cloud-fan

sql/hive/src/test/scala/org/apache/spark/sql/hive/HiveExternalCatalogVersionsSuite.scala

@@ -22,6 +22,7 @@ import java.nio.charset.StandardCharsets
 import java.nio.file.{Files, Paths}
 
 import scala.sys.process._
+import scala.util.control.NonFatal
 
 import org.apache.hadoop.conf.Configuration
 
@@ -169,6 +170,10 @@ class HiveExternalCatalogVersionsSuite extends SparkSubmitTestUtils {
       """.stripMargin.getBytes("utf8"))
     // scalastyle:on line.size.limit
 
+    if (PROCESS_TABLES.testingVersions.isEmpty) {
+      fail("Fail to get the lates Spark versions to test.")
+    }
+
     PROCESS_TABLES.testingVersions.zipWithIndex.foreach { case (version, index) =>
       val sparkHome = new File(sparkTestingDir, s"spark-$version")
       if (!sparkHome.exists()) {
@@ -206,7 +211,19 @@ class HiveExternalCatalogVersionsSuite extends SparkSubmitTestUtils {
 
 object PROCESS_TABLES extends QueryTest with SQLTestUtils {
   // Tests the latest version of every release line.
-  val testingVersions = Seq("2.3.3", "2.4.2")
+  val testingVersions: Seq[String] = {
+    import scala.io.Source
+    try {
+      Source.fromURL("https://dist.apache.org/repos/dist/release/spark/").mkString
+        .split("\n")
+        .filter(_.contains("""<li><a href="spark-"""))
+        .map("""<a href="spark-(\d.\d.\d)/">""".r.findFirstMatchIn(_).get.group(1))
+        .filter(_ < org.apache.spark.SPARK_VERSION)
+    } catch {
+      // do not throw exception during object initialization.
+      case NonFatal(_) => Nil
+    }
+  }
 
   protected var spark: SparkSession = _