<i18n dev> RFR: 8355522: Remove the `java.locale.useOldISOCodes` system property

[Naoto Sato]

This PR removes the system property deprecated in JDK 25. If the property is specified at runtime, a warning will be emitted at startup to inform the user that the value is ignored. A corresponding CSR has been drafted as well

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/26419/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26419&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355522
  Stats: 93 lines in 6 files changed: 1 ins; 61 del; 31 mod
  Patch: https://git.openjdk.org/jdk/pull/26419.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26419/head:pull/26419

PR: https://git.openjdk.org/jdk/pull/26419