RFR: 8307068: store a JavaThread* in the java.lang.Thread object after the JavaThread* is added to the main ThreadsList [v4]

[Daniel D. Daugherty]

> A small fix to store a JavaThread* in the java.lang.Thread object after the JavaThread*
> is added to the main ThreadsList. Also adds the following:
> - `java_lang_Thread::thread_acquire()`
> - `java_lang_Thread::release_set_thread()`
> 
> And uses them on an as-needed basis.

Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:

  dholmes CR - update comments and switch from java_lang_Thread::set_thread() to release_set_thread().

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13723/files
  - new: https://git.openjdk.org/jdk/pull/13723/files/ff0faa62..4385c113

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13723&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13723&range=02-03

  Stats: 7 lines in 1 file changed: 3 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13723.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13723/head:pull/13723

PR: https://git.openjdk.org/jdk/pull/13723