[jdk21u] Integrated: 8315702: jcmd Thread.dump_to_file slow with millions of virtual threads

[Rob McKenna]

backport 8315702

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Commit messages:
 - Backport 3c258ac907287850d690375bae07c0575d1f1463

Changes: https://git.openjdk.org/jdk21u/pull/170/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=170&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315702
  Stats: 19 lines in 1 file changed: 8 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/jdk21u/pull/170.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/170/head:pull/170

PR: https://git.openjdk.org/jdk21u/pull/170