RFR: 8306738: Select num workers for safepoint ParallelCleanupTask

Mon Apr 24 12:12:03 UTC 2023

Select num workers for safepoint ParallelCleanupTask to be at most the number of parallel cleanup tasks `SAFEPOINT_CLEANUP_NUM_TASKS`

Unsure if `WorkerThreads::max_workers()` is more correct than `WorkerThreads::created_workers()` or `WorkerThreads::active_workers()`. 

Tested tier1-3 Oracle platforms.

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Commit messages:
 - 8306738: Select num workers for safepoint ParallelCleanupTask

Changes: https://git.openjdk.org/jdk/pull/13616/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13616&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306738
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13616.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13616/head:pull/13616

PR: https://git.openjdk.org/jdk/pull/13616