[jdk21u] RFR: 8315683: Parallelize java/util/concurrent/tck/JSR166TestCase.java

[Soumadipta Roy]

Backport 4415261688dc258b6d254668bcf8818c61cc65ea to JDK21u.

Backporting the fix for https://bugs.openjdk.org/browse/JDK-8315683 merged as part of https://github.com/openjdk/jdk/pull/15619. https://github.com/openjdk/jdk/commit/4415261688dc258b6d254668bcf8818c61cc65ea.patch could be cleanly applied.

The tests passed in release mode in linux_x86_64 with time: **611.98s user 25.42s system 1440% cpu 44.259 total**
Before it was: **333.50s user 19.46s system 564% cpu 1:02.55 total**

Passed: java/util/concurrent/tck/JSR166TestCase.java#default
Passed: java/util/concurrent/tck/JSR166TestCase.java#security-manager
Passed: java/util/concurrent/tck/JSR166TestCase.java#others
Passed:
java/util/concurrent/tck/JSR166TestCase.java#forkjoinpool-common-parallelism
Test results: passed: 4

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Commit messages:
 - 8315683: Parallelize java/util/concurrent/tck/JSR166TestCase.java

Changes: https://git.openjdk.org/jdk21u/pull/195/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=195&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315683
  Stats: 34 lines in 1 file changed: 27 ins; 4 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u/pull/195.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/195/head:pull/195

PR: https://git.openjdk.org/jdk21u/pull/195