Scala 2.13 support. (#9099)

1. Updated the test logic
2. Added smoke tests for Spark examples.
3. Added integration tests for Spark with Scala 2.13

jvm-packages/xgboost4j-flink/pom.xml

@@ -5,9 +5,11 @@
     <modelVersion>4.0.0</modelVersion>
     <parent>
         <groupId>ml.dmlc</groupId>
-        <artifactId>xgboost-jvm_2.12</artifactId>
+        <artifactId>xgboost-jvm</artifactId>
         <version>2.0.0-SNAPSHOT</version>
     </parent>
+
+    <name>xgboost4j-flink</name>
     <artifactId>xgboost4j-flink_${scala.binary.version}</artifactId>
     <version>2.0.0-SNAPSHOT</version>
     <properties>