RFR: 8318608: Enable parallelism in vmTestbase/nsk/stress/threads tests

[Elif Aslan]

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

Below are the before and after test run comparisons:

Before:
 time,count
   15,    1
   33,    1
   48,    1
   66,    1
   72,    1
   77,    1

Mean                51.83s
Standard deviation  22.24s
Total elapsed time 1m 17s

After:
 time,count
   19,    1
   23,    1
   29,    1
   34,    1
   48,    1
   53,    1

Mean                34.33s
Standard deviation  12.43s
Total elapsed time 0m 53s

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

Commit messages:
 - JDK-8315937: Enable parallelism in vmTestbase/nsk/stress/threads tests

Changes: https://git.openjdk.org/jdk/pull/16327/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16327&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318608
  Stats: 24 lines in 1 file changed: 0 ins; 24 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16327.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16327/head:pull/16327

PR: https://git.openjdk.org/jdk/pull/16327