<i18n dev> RFR: 8343777: Add since checker tests to Internationalisation modules

[Nizar Benalla]

Can I please get a review for this PR that add tests to verify the value of `@since` tags to the Internationalisation area modules. The test is described in this [email](https://mail.openjdk.org/pipermail/jdk-dev/2024-October/009474.html).

The benefit from this is helping API authors and reviewer validate the accuracy of `@since` in their source code (and subsequently, in the generated documentation). And lessen the burden on Reviewers.

The test has been added for `java.base` and a few other modules and has helped catch some bugs before they make it to the JDK.

TIA

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Commit messages:
 - remove backticks
 - Add two new jtreg tests.

Changes: https://git.openjdk.org/jdk/pull/21985/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21985&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343777
  Stats: 6 lines in 2 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/21985.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21985/head:pull/21985

PR: https://git.openjdk.org/jdk/pull/21985