[jdk11u-dev] RFR: 8315442: Enable parallelism in vmTestbase/nsk/monitoring/stress/thread tests

[Andrew Lu]

I backport this for parity with 11.0.25-oracle.

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Commit messages:
 - Backport 9013b032448518e09a7c6f2e80054be722c970a3

Changes: https://git.openjdk.org/jdk11u-dev/pull/2760/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2760&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315442
  Stats: 483 lines in 21 files changed: 0 ins; 483 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2760.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2760/head:pull/2760

PR: https://git.openjdk.org/jdk11u-dev/pull/2760