<i18n dev> RFR: 8355522: Remove the `java.locale.useOldISOCodes` system property [v2]

[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

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  Reflects review comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26419/files
  - new: https://git.openjdk.org/jdk/pull/26419/files/85d8adfb..bcfd8a7e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26419&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26419&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 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