[jdk21u] RFR: 8316142: Enable parallelism in vmTestbase/nsk/monitoring/stress/lowmem tests

[Aleksey Shipilev]

Clean backport to improve tests performance. The change was in mainline for several weeks, and no bugtail was recorded.

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Commit messages:
 - Backport 4421951d8f1c6fb16255851a803252fe96a453e5

Changes: https://git.openjdk.org/jdk21u/pull/304/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=304&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/jdk21u/pull/304.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/304/head:pull/304

PR: https://git.openjdk.org/jdk21u/pull/304