[jdk11u-dev] RFR: 8315937: Enable parallelism in vmTestbase/nsk/stress/numeric tests

[Soumadipta Roy]

Backporting the fix for https://bugs.openjdk.org/browse/JDK-8315937 merged as part of https://github.com/openjdk/jdk/pull/15725. https://github.com/openjdk/jdk/commit/eb1f67b160c4d2b8feb7330786ecd8e53ed53946.patch could be applied cleanly.

Below are the results:
* before_release: **150.44s user 11.33s system 552% cpu 29.291 total**
* before_fastdebug: **390.49s user 14.77s system 952% cpu 42.535 total**
* after_release: **152.51s user 11.60s system 592% cpu 27.716 total**
* after_fastdebug: **348.22s user 12.40s system 929% cpu 38.792 total**

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Commit messages:
 - Backport 339034c150cad7d3e1df55dbfac6c2b7746c4f92

Changes: https://git.openjdk.org/jdk11u-dev/pull/2156/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2156&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315937
  Stats: 24 lines in 1 file changed: 0 ins; 24 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2156.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2156/head:pull/2156

PR: https://git.openjdk.org/jdk11u-dev/pull/2156