[jdk17u-dev] RFR: 8316608: Enable parallelism in vmTestbase/gc/vector tests

[Soumadipta Roy]

Backporting the fix for https://bugs.openjdk.org/browse/JDK-8316608 merged as part of openjdk/jdk#16028.
https://github.com/openjdk/jdk/commit/f61499c73fe03e2e3680d7f58a84183364c5c5ac.patch could be applied cleanly.

Run details on AL2_x86_64:

before: 3518.69s user 84.97s system 840% cpu 7:08.71 total
after: 6176.30s user 112.25s system 3753% cpu 2:47.54 total

before: 1373.06s user 135.80s system 373% cpu 6:44.35 total
after: 4479.07s user 305.63s system 3370% cpu 2:21.95 total

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Commit messages:
 - Backport f61499c73fe03e2e3680d7f58a84183364c5c5ac

Changes: https://git.openjdk.org/jdk17u-dev/pull/2337/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2337&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316608
  Stats: 299 lines in 13 files changed: 0 ins; 299 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2337.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2337/head:pull/2337

PR: https://git.openjdk.org/jdk17u-dev/pull/2337