While trying out some a fix for [JDK-8386278](https://bugs.openjdk.org/browse/JDK-8386278) I noticed there's no concurrency stress test for ConcurrentSkipListMap. This existing test is already suitable, it just needs a specific case added.
--------- - [x] I confirm that I make this contribution in accordance with the [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). ------------- Commit messages: - Add test-case for ConcurrentSkipListMap Changes: https://git.openjdk.org/jdk/pull/31462/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=31462&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8386372 Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/31462.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/31462/head:pull/31462 PR: https://git.openjdk.org/jdk/pull/31462
