[jdk21u-dev] RFR: 8330846: Add stacks of mounted virtual threads to the HotSpot thread dump

[Jiawei Tang]

I have two reasons to backport 8330846.
1. When run the jtreg test `test/jdk/jdk/jfr/event/runtime/TestThreadDumpEvent.java`  with the option `-testThreadFactory:Virtual`, it will fail because of the loss of `TestThreadDumpEvent.main` in the result.
2. It helps developers to have a better view of their programs.

-------------

Commit messages:
 - Backport fcedde804277af5a26febdcfb7817858d72f01ab

Changes: https://git.openjdk.org/jdk21u-dev/pull/1129/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1129&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330846
  Stats: 97 lines in 2 files changed: 97 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1129.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1129/head:pull/1129

PR: https://git.openjdk.org/jdk21u-dev/pull/1129