RFR: 8315442: Enable parallelism in vmTestbase/nsk/monitoring/stress/thread tests

[Aleksey Shipilev]

Current vmTestbase/nsk/monitoring/stress/thread tests contains 21 tests, each running exclusively. This drags the tier4 test times up. There seem to be no reason to run these tests exclusively, though: they complete in reasonable time, are lightly-threaded, and consume the usual amount of memory.

We should consider enabling parallelism for them and get improved test performance. Currently it is blocked by TEST.properties with exclusiveAccess.dirs directives in them.

Current run on 18-core machine:
 1025.63s user 97.23s system 586% cpu 3:11.60 total

Fully parallel:
 1125.04s user 107.60s system 1583% cpu 1:17.83 total 

Additional testing:
 - [x]  50x iterations of Linux x86_64 fastdebug `vmTestbase/nsk/monitoring/stress/thread`

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/15508/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15508&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315442
  Stats: 483 lines in 21 files changed: 0 ins; 483 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15508.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15508/head:pull/15508

PR: https://git.openjdk.org/jdk/pull/15508