Test with Java 25 and Java 21 (#1352)

Java 25 released in September 2025 and the Jenkins project wants to
support it soon after release.  Run plugin tests with Java 25 and Java 21.
Java 17 byte code continues to be generated by the Java 21 and Java 25
compilers based on the configuration of the plugin pom.

Testing done:

* Confirmed that automated tests pass with Java 25

Author: MarkEWaite

Jenkinsfile

@@ -8,6 +8,6 @@ buildPlugin(
   useContainerAgent: false,
   failFast: false,
   configurations: [
-    [platform: 'linux', jdk: 21],
-    [platform: 'windows', jdk: 17],
+    [platform: 'linux', jdk: 25],
+    [platform: 'windows', jdk: 21],
 ])