New candidate JEP: 506: Scoped Values

[Mark Reinhold]

https://openjdk.org/jeps/506

  Summary: Introduce scoped values, which enable a method to share
  immutable data both with its callees within a thread, and with child
  threads.  Scoped values are easier to reason about than thread-local
  variables.  They also have lower space and time costs, especially when
  used together with virtual threads (JEP 444) and structured concurrency
  (JEP 505).

- Mark