RFR: 8316608: Enable parallelism in vmTestbase/gc/vector tests

[Soumadipta Roy]

The commit includes changes to unblock parallelism for more `hotspot:tier4` tests. in `vmTestbase/gc/vector` tests.

Below are the before and after run comparisons:
* before_fastdebug: **3480.71s user 83.97s system 830% cpu 7:09.41 total**
* before_release: **1369.61s user 147.03s system 371% cpu 6:48.63 total**
* after_fastdebug: **2214.52s user 63.19s system 2374% cpu 1:35.94 total**
* after_release: **1130.28s user 110.97s system 2478% cpu 50.089 total**

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Commit messages:
 - 8316608: Enable parallelism in vmTestbase/gc/vector tests

Changes: https://git.openjdk.org/jdk/pull/16028/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16028&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/jdk/pull/16028.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16028/head:pull/16028

PR: https://git.openjdk.org/jdk/pull/16028