Support JDK-20 builds on Jenkins

[reta]

Is your feature request related to a problem? Please describe

JDK-19 is superseded by JDK-20

Describe the solution you'd like

Make JDK-20 available on Jenkins so we could start using it in Gradle checks.

Describe alternatives you've considered

N/A

Additional context

Depends on opensearch-project/OpenSearch#6792

[reta]

@peterzhuamazon I wil pick this one up if you don't mind

[peterzhuamazon]

Hi @reta are we ok to wait until JDK21 release?
JDK21 is LTS and it will be released on September.
Thanks.

[reta]

Hi @reta are we ok to wait until JDK21 release?

I think we could in general, but we need to:

• update bundled JDK to JDK-20 (we cannot supply unsupported version)
• make sure all test passes under JDK-20

I will update the issue shortly if the JDK-20 is really needed on CI, thanks!

[reta]

@peterzhuamazon I just did test run against JDK-20 and it seems like we do have some code paths that use unsupported APIs (like Thread::resume, at least in tests), I think it would be beneficial to add JDK-20 support to CI and be ready for JDK-21

[peterzhuamazon]

So @reta we need to ship JDK20 in bundle right now?

[peterzhuamazon]

Please also send a PR to change JDK on opensearch-ci so we can do the deployment of new AMIs.

[reta]

So @reta we need to ship JDK20 in bundle right now?

I think it would be better to do it now, since it does require code changes sadly