[jdk17u-dev] RFR: 8276696: ParallelObjectIterator freed at the wrong time in VM_HeapDumper

[Aleksey Shipilev]

Unclean backport to improve the heap dumping code for cleaner [JDK-8307348](https://bugs.openjdk.org/browse/JDK-8307348) backport. This backport is not clean, because it misses the parts of HeapDumper introduced by [JDK-8252842](https://bugs.openjdk.org/browse/JDK-8252842), which I don't want to backport at all in 17u, given the large bugtail for it.

Additional testing:
 - [x] Linux x86_64 fastdebug `jdk/jfr serviceability/sa`
 - [ ] Linux x86_64 fastdebug `tier1 tier2 tier3`
 - [ ] Linux AArch64 fastdebug `tier1 tier2 tier3`

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Commit messages:
 - Backport f4dc03ea6de327425ff265c3d2ec16ea7b0e1634

Changes: https://git.openjdk.org/jdk17u-dev/pull/1440/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1440&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8276696
  Stats: 57 lines in 14 files changed: 28 ins; 6 del; 23 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1440.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1440/head:pull/1440

PR: https://git.openjdk.org/jdk17u-dev/pull/1440