RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v10]

[Per Minborg]

> Implement JEP 502.
> 
> The PR passes tier1-tier3 tests.

Per Minborg has updated the pull request incrementally with two additional commits since the last revision:

 - Remove snippet for orElseSet
 - Add partial equality test

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23972/files
  - new: https://git.openjdk.org/jdk/pull/23972/files/69688848..8b4113f6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23972&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23972&range=08-09

  Stats: 26 lines in 2 files changed: 9 ins; 13 del; 4 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