[jdk21u-dev] RFR: 8321206: Make Locale related system properties `StaticProperty`

[Ben Taylor]

Clean backport of change to make Locale system properties static.

>From the original PR:
>Currently, Locale-related system properties, such as user.language or user.country, are initialized when the Locale class is loaded. Making them static properties is safer than relying on the Locale class loading timing, which could potentially be changed depending on the implementation.

This change also makes [JDK-8321940](https://bugs.openjdk.org/browse/JDK-8321940) clean, which will improve maintainability by reducing the number of manually curated `ADD_EXCL` entries in `cdsHeapVerifier.cpp`.

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Commit messages:
 - Backport 0c178beb69c4c5fc3e92621340748e42d017d458

Changes: https://git.openjdk.org/jdk21u-dev/pull/912/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=912&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321206
  Stats: 69 lines in 3 files changed: 49 ins; 7 del; 13 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/912.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/912/head:pull/912

PR: https://git.openjdk.org/jdk21u-dev/pull/912