Investigate Java 21 and Jruby compatibility

[roaksoax]

Java 21 is now available and we would like to make it the default for Logstash. However, we need to investigate whether it is possible provided Jruby supports it.

Deprecation list: https://docs.oracle.com/en/java/javase/21/docs/api/deprecated-list.html Dependant tasks:

• [ ] Fix argument error in JRuby and JDK 21 https://github.com/jruby/jruby/issues/8061

Depending tasks:

• [ ] Update Derby https://github.com/logstash-plugins/logstash-integration-jdbc/pull/148

Other Tasks

• [ ] Test and verify all plugins are supported on newer JDK21 (with current jruby).
• [ ] Bundle JDK 21 and fix all TODO related to getId been deprecated in JDK 19 and replaced by threadId() starting from JDK 21