RFR: 8318607: Enable parallelism in vmTestbase/nsk/stress/jni tests

[Elif Aslan]

The commit includes changes to unblock parallelism for more `hotspot:tier4 `tests. in `test/hotspot/jtreg/vmTestbase/nsk/stress/jni `tests.

Below are the before and after test run comparisons:

Before:
 time,count
   32,    1
   63,    1
   64,    1
   94,    1
  124,    1
  155,    1
  185,    1
  216,    1

Mean               116.63s
Standard deviation  60.62s
Total elapsed time 3m 36s

After:
 time,count
    4,    1
   33,    1
   34,    2
   36,    3
   41,    1

Mean                31.75s
Standard deviation  10.73s
Total elapsed time 0m 41s

-------------

Commit messages:
 - JDK-8318607:Enable parallelism in vmTestbase/nsk/stress/jni tests

Changes: https://git.openjdk.org/jdk/pull/16326/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16326&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318607
  Stats: 24 lines in 1 file changed: 0 ins; 24 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16326.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16326/head:pull/16326

PR: https://git.openjdk.org/jdk/pull/16326