RFR: 8319376: Parallel: Forwarded objects during heap inspection

[Roman Kennke]

See JBS issue for details.

Testing:
 - [x] gc/logging/TestUnifiedLoggingSwitchStress.java -XX:+UseParallelGC
 - [ ] tier1 -XX:+UseParallelGC
 - [ ] tier2 -XX:+UseParallelGC
 - [ ] hotspot_gc

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Commit messages:
 - 8319376: Parallel: Forwarded objects during heap inspection

Changes: https://git.openjdk.org/jdk/pull/16494/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16494&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319376
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16494.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16494/head:pull/16494

PR: https://git.openjdk.org/jdk/pull/16494