[jdk11u-dev] RFR: 8318605: Enable parallelism in vmTestbase/nsk/stress/stack tests

[Daniel Hu]

Clean backport to make vmTestbase/nsk/stress/stack tests parallel

Ran `make run-test TEST=vmTestbase/nsk/stress/stack JTREG=REPEAT_COUNT=10`
Before:
`549.91s user 42.27s system 261% cpu 3:46.34 total`
After:
`542.52s user 40.49s system 379% cpu 2:33.50 total`

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Commit messages:
 - Backport d9aa1deac8474f87dd867809f7265b9496917c6f

Changes: https://git.openjdk.org/jdk11u-dev/pull/3024/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=3024&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318605
  Stats: 24 lines in 1 file changed: 0 ins; 24 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/3024.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/3024/head:pull/3024

PR: https://git.openjdk.org/jdk11u-dev/pull/3024