RFR: 8355536: Create version constants to model preview language and vm features [v8]

[Chen Liang]

> Sometimes, for version-specific feature access APIs, we wish to access the preview features of the current Java SE release. To reduce the impact of adding one preview-specific version on every site, we can add a constant modeling the preview features as a fake version.

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  Fixes

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25017/files
  - new: https://git.openjdk.org/jdk/pull/25017/files/0f9c501c..b39504fc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25017&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25017&range=06-07

  Stats: 15 lines in 3 files changed: 3 ins; 6 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/25017.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25017/head:pull/25017

PR: https://git.openjdk.org/jdk/pull/25017