[VL] Delete global reference to a class object in JNI unload

[philo-he]

What changes were proposed in this pull request?

The global reference to class object of NativePlanValidationInfo was introduced in #9092. It should be explicitly deleted in JNI unload.

[github-actions]

Thanks for opening a pull request!

Could you open an issue for this pull request on Github Issues?

https://github.com/apache/incubator-gluten/issues

Then could you also rename commit message and pull request title in the following format?

[GLUTEN-${ISSUES_ID}][COMPONENT]feat/fix: ${detailed message}

See also:

• Other pull requests

[philo-he]

@jackylee-ch, could you please take a look?

[zhztheplayer]

@philo-he Have you met any issue without the patch?

[philo-he]

@zhztheplayer, no, seems this reference cannot be auto deleted, right? And I note all created global reference in our code are explicitly deleted when JNI is unloading.

[zhztheplayer]

@zhztheplayer, no, seems this reference cannot be auto deleted, right?

For now, actually the unloading is invoked only when JVM is shutting down, so it's not a big deal whether we explicitly delete them at that time. But it's good to keep a consistent form of code. I was just curious whether there was an error or so.