JDK24 removes CallersHolder for Java17SystemExitToggle

We bumped to Java24 and started to hit: "Failed to load Java 17 system exit override"

I no longer see this `private static class` in JDK24: https://github.com/openjdk/jdk24u/blob/master/src/java.base/share/classes/java/lang/System.java

Relevant line:
https://github.com/bazel-contrib/rules_jvm/blob/5ba4ba2b4e44eab9201c53cb5d87e87499f6cc28/java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/Java17SystemExitToggle.java#L17C60-L17C73

Start with java/src/com/github/bazel_contrib/contrib_rules_jvm/junit5/Java17SystemExitToggle.java, especially the referenced line, and compare its JDK17 assumptions with the JDK24 System.java source linked in the issue. Reproduce the "Failed to load Java 17 system exit override" failure and confirm the JUnit5 integration works with Java24 without relying on the removed CallersHolder.

Written by the indexing model from the issue text.