RFR: 8315437: Enable parallelism in vmTestbase/nsk/monitoring/stress/classload tests

[Aleksey Shipilev]

Current vmTestbase/nsk/monitoring/stress/classload tests contains 24 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:
2011.95s user 201.83s system 356% cpu 10:20.19 total

Fully parallel:
2274.02s user 128.64s system 2029% cpu 1:58.39 total 

Additional testing:
 - [ ] 100x iterations of Linux x86_64 fastdebug `vmTestbase/nsk/monitoring/stress/classload`

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/15506/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15506&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315437
  Stats: 552 lines in 24 files changed: 0 ins; 552 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15506.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15506/head:pull/15506

PR: https://git.openjdk.org/jdk/pull/15506