RFR: 8280397: Factor out task queue statistics printing

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that makes task queue (set) printing available in a central place so that not every user needs to reinvent the wheel?
As example I wired up existing G1/Parallel GC young collection statistics printing, but I intend to add this for full gcs too; since ZGC and Shenandoah do not print task queues at all I do not intend to do that at least initially.
Currently the main printing method is in `CollectedHeap`, but I can move it elsewhere if needed (all but Serial GC do use task queue sets though, so.....).

Testing: gha (building), local testing

Thanks,
  Thomas

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Commit messages:
 - Initial implementation using CollectedHeap

Changes: https://git.openjdk.java.net/jdk/pull/7174/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7174&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280397
  Stats: 138 lines in 8 files changed: 68 ins; 64 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7174.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7174/head:pull/7174

PR: https://git.openjdk.java.net/jdk/pull/7174