[jdk11u-dev] RFR: 8316142: Enable parallelism in vmTestbase/nsk/monitoring/stress/lowmem tests

[Alexandru C. Moraru]

Clean backport to improve tests performance.

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Commit messages:
 - Backport 4421951d8f1c6fb16255851a803252fe96a453e5

Changes: https://git.openjdk.org/jdk11u-dev/pull/2703/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2703&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316142
  Stats: 828 lines in 36 files changed: 0 ins; 828 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2703.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2703/head:pull/2703

PR: https://git.openjdk.org/jdk11u-dev/pull/2703