Test with Java 21 (#736)

* Add a JDK21 Jenkinsfile for ci.jenkins.io

* Update Jenkinsfile

Author: gounthar

Jenkinsfile

@@ -1,4 +1,10 @@
-buildPlugin(useContainerAgent: true, configurations: [
-  [platform: 'linux', jdk: 17],
-  [platform: 'windows', jdk: 11],
+/*
+ See the documentation for more options:
+ https://github.com/jenkins-infra/pipeline-library/
+*/
+buildPlugin(
+  useContainerAgent: true, // Set to `false` if you need to use Docker for containerized tests
+  configurations: [
+    [platform: 'linux', jdk: 21],
+    [platform: 'windows', jdk: 17],
 ])