RFR: 8332923: ObjectMonitorUsage.java failed with unexpected waiter_count [v2]

[SendaoYan]

> Hi all,
>   ObjectMonitorUsage.java failed with `unexpected waiter_count` after [JDK-8328083](https://bugs.openjdk.org/browse/JDK-8328083) on linux x86_32. It should be predicated with `@requires vm.continuations` to be skipped.
> 
> Additional testing:
> - [x] linux x86_32, test has been skiped.
> - [x] linux x86_64, test still work.

SendaoYan has updated the pull request incrementally with one additional commit since the last revision:

  1. java_lang_VirtualThread::is_instance(thread_oop) -> thread_oop->is_a(vmClasses::BaseVirtualThread_klass()); 2. calculating nWant(mon->contentions())

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19405/files
  - new: https://git.openjdk.org/jdk/pull/19405/files/4a4326cc..ea28c232

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19405&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19405&range=00-01

  Stats: 14 lines in 2 files changed: 8 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/19405.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19405/head:pull/19405

PR: https://git.openjdk.org/jdk/pull/19405