Rebasing the JVMS/JLS revisions onto that of current release (20)

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Hi,
Just a heads up, I am glad to see active developments in the
specification for various Valhalla JEPs on Dan's code review site
https://cr.openjdk.org/~dlsmith/jep401/jep401-20230519/

I recommend upgrading them to Java 20, as they appear to be based of
Java 16's specifications, as shown by the absence of
PermittedSubclasses attribute.

In addition, these JVMS changes for https://openjdk.org/jeps/8267650
Better-defined JVM class file validation appear quite mature already.
Is there any outstanding problem that obstructs their progress? This
would prove helpful for future Language and VM changes, just like how
Nestmates, initially aimed for generic specialization, immediately
eliminated synthetic bridge methods across inner classes for all Java
programs.

Best,
Chen Liang