RFR: 8351565: Implement JEP 502: Stable Values (Preview)

[Per Minborg]

Implement JEP 502.

The PR passes tier1-tier3 tests.

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Commit messages:
 - Use acquire semantics for reading rather than volatile semantics
 - Add missing null check
 - Simplify handling of sentinel, wrap, and unwrap
 - Fix JavaDoc issues
 - Fix members in StableEnumFunction
 - Address some comments in the PR
 - Merge branch 'master' into implement-jep502
 - Revert change
 - Fix copyright issues
 - Update JEP number
 - ... and 231 more: https://git.openjdk.org/jdk/compare/4cf63160...09ca44e6

Changes: https://git.openjdk.org/jdk/pull/23972/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23972&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351565
  Stats: 3980 lines in 30 files changed: 3949 ins; 18 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/23972.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23972/head:pull/23972

PR: https://git.openjdk.org/jdk/pull/23972