[28] JEP 401: Value Classes and Objects (Preview)

Ref: https://bugs.openjdk.org/browse/JDK-8251554
https://cr.openjdk.org/~dlsmith/jep401/latest/

also ref: (as mentioned in https://download.java.net/java/early_access/jdk28/docs/specs/value-objects-jls.html)

- [JVMS Changes](https://download.java.net/java/early_access/jdk28/docs/specs/value-objects-jvms.html)
- [JVMS Changes for Strict Fields](https://download.java.net/java/early_access/jdk28/docs/specs/strict-fields-jvms.html)

sub-issues:

- [x] https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/7189
- [x] https://github.com/eclipse-jdt/eclipse.jdt.core/issues/4890
- [ ] #5088
- [ ] more to be added...