Spec change documents for Value Objects

[Dan Smith]

Please see these two spec change documents for JLS and JVMS changes in support of the Value Objects feature.

http://cr.openjdk.java.net/~dlsmith/jep8277163/jep8277163-20220427/specs/value-objects-jls.html
http://cr.openjdk.java.net/~dlsmith/jep8277163/jep8277163-20220427/specs/value-objects-jvms.html

These are synced up with the latest iteration of the draft JEP, found here:
https://openjdk.java.net/jeps/8277163

I've applied the changes we discussed recently on this list:
- Replacing the 'IdentityObject' and 'ValueObject' interfaces with class modifiers
- Updating the treatment of class 'Object' so that it can continue to be instantiated
- Solidified the details of special '<vnew>' instance creation methods

The JVMS document is layered on top of some JVMS cleanups that I need to circle back on (mostly as part of separate JEP https://openjdk.java.net/jeps/8267650).

I think we've reached a point where it's worth getting these production-ready. Please let me know if you notice missing pieces, think something needs better treatment, or just catch a typo. Thanks!