RFR: 8324755: Enable parallelism in vmTestbase/gc/gctests/LargeObjects tests

[Soumadipta Roy]

The commit includes changes to unblock parallelism in vmTestbase/gc/gctests/LargeObjects tests.

Below are the before and after run comparisons on AL2:

# Fastdebug
before: 7985.84s user 417.77s system 498% cpu 28:06.25 total
after: 2503.22s user 48.65s system 606% cpu 7:00.69 total

# Release
before: 1063.25s user 45.87s system 125% cpu 14:42.10 total
after: 1077.70s user 45.71s system 481% cpu 3:53.28 total

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Commit messages:
 - 8324755: Enable parallelism in vmTestbase/gc/gctests/LargeObjects tests

Changes: https://git.openjdk.org/jdk/pull/18798/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18798&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324755
  Stats: 115 lines in 5 files changed: 0 ins; 115 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18798.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18798/head:pull/18798

PR: https://git.openjdk.org/jdk/pull/18798