Add Java 24 into the test matrix

[Goooler]

Description

The latest JDK version should be checked on.

Checklist

• New code follows the Google Java Style Guide
  This is automatically checked by mvn verify, but can also be checked on its own using mvn spotless:check.
  Style violations can be fixed using mvn spotless:apply; this can be done in a separate commit to verify that it did not cause undesired changes.
• If necessary, new public API validates arguments, for example rejects null
• New public API has Javadoc
  • Javadoc uses @since $next-version$
    ($next-version$ is a special placeholder which is automatically replaced during release)
• If necessary, new unit tests have been added
  • Assertions in unit tests use Truth, see existing tests
  • No JUnit 3 features are used (such as extending class TestCase)
  • If this pull request fixes a bug, a new test was added for a situation which failed previously and is now fixed
• mvn clean verify javadoc:jar passes without errors

[Goooler]

 [proguard] ProGuard, version 7.7.0
 [proguard] Unexpected error
 [proguard] java.io.IOException: Can't read [/opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/24.0.0-36/x64/jmods/java.base.jmod] (No such file or directory: /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/24.0.0-36/x64/jmods/java.base.jmod)
 [proguard] 	at proguard.InputReader.readInput(InputReader.java:282) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	at proguard.InputReader.readInput(InputReader.java:229) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	at proguard.InputReader.readInput(InputReader.java:206) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	at proguard.InputReader.execute(InputReader.java:157) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	at proguard.pass.PassRunner.run(PassRunner.java:24) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	at proguard.ProGuard.readInput(ProGuard.java:336) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	at proguard.ProGuard.execute(ProGuard.java:123) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	at proguard.ProGuard.main(ProGuard.java:649) [proguard-base-7.7.0.jar:7.7.0]
 [proguard] Caused by: java.io.IOException: No such file or directory: /opt/hostedtoolcache/Java_Temurin-Hotspot_jdk/24.0.0-36/x64/jmods/java.base.jmod
 [proguard] 	at proguard.io.DirectorySource.pumpDataEntries(DirectorySource.java:41) ~[proguard-core-9.1.10.jar:7.7.0]
 [proguard] 	at proguard.InputReader.readInput(InputReader.java:278) ~[proguard-base-7.7.0.jar:7.7.0]
 [proguard] 	... 7 more

No idea about this...

[eamonnmcmanus]

Thanks for the suggestion! We currently only test Long Term Support (LTS) releases of Java. When Java 25 comes out in September, we'll probably add that. It might be that ProGuard will need to be updated for Java 25; I'm not sure what the failure you saw means either.

[Marcono1234]

ProGuard failure seems to be related to https://adoptium.net/blog/2025/03/eclipse-temurin-jdk24-JEP493-enabled/, see also Guardsquare/proguard#473

I would also suggest to wait with JDK 24 (or newer) build support, and wait on the outcome of the issue with ProGuard.