<i18n dev> RFR: 8358426: Improve lazy computation in Locale

[Justin Lu]

Please review this PR which improves occurrences of lazy computation in `Locale` and `BaseLocale`.

Existing lazy initialization strategies such as CHM, static nested class, and local inner class are replaced with Stable Values.

Lambda usage is intentionally avoided in this change during `Locale` creation and in static fields due to potential startup performance degradation as noted by [JDK-8331932](https://bugs.openjdk.org/browse/JDK-8331932).

Rather than convert `iso3166CodesMap` to a Stable Map, each ISO 3166 resource is represented as a SV. Also, I did not think it was necessary to maintain a SV for _both_ the array and set of ISO3166-1 alpha-2 codes.

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Commit messages:
 - init

Changes: https://git.openjdk.org/jdk/pull/25646/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25646&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358426
  Stats: 151 lines in 2 files changed: 51 ins; 59 del; 41 mod
  Patch: https://git.openjdk.org/jdk/pull/25646.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25646/head:pull/25646

PR: https://git.openjdk.org/jdk/pull/25646