RFR: 8305670: Performance regression in LockSupport.unpark with lots of idle threads [v9]

[Daniel D. Daugherty]

> Address the performance regression in `LockSupport.unpark()` with the following changes:
> - Add `FastThreadsListHandle` helper class to threadSMR.[ch]pp for quickly determining if a JavaThread* is protected by the ThreadsListHandle embedded in the new helper object.
> - Update `Unsafe_Unpark()` to pass `java_lang_Thread::thread_acquire(thread_oop)` to a new instance of the `FastThreadsListHandle` object and only do the unpark work if the target JavaThread* is protected.

Daniel D. Daugherty has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 10 commits:

 - Merge branch 'JDK-8307068' into JDK-8305670
 - dholmes CR - FastThreadsListHandle ctr should use java_lang_Thread::thread() instead of java_lang_Thread::thread_acquire(); clarify comments.
 - Merge branch 'JDK-8307068' into JDK-8305670
 - Merge JDK-8305670 with code review changes in JDK-8307068.
 - Merge branch 'JDK-8307068' into JDK-8305670
 - Merge branch 'jdk-21+20' into JDK-8305670
 - 8305670.with-rehn-quick-mode.cr3.patch
 - Use optimized logic in Unsafe_Unpark() instead of cv_internal_thread_to_JavaThread().
 - dholmes CR - add more comments.
 - 8305670.with-rehn-quick-mode.cr0.patch

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

Changes: https://git.openjdk.org/jdk/pull/13519/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13519&range=08
  Stats: 53 lines in 3 files changed: 39 ins; 1 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/13519.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13519/head:pull/13519

PR: https://git.openjdk.org/jdk/pull/13519