RFR: 8307483: New micros for j.u.c.LockSupport [v4]

[Eric Caspole]

> These micros were developed while investigating JDK-8305670 by myself and Sergey Kuksenko. The order of thread creation was important in that bug, so there are 2 JMH for creating sleepers before and after the worker threads.

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

  Apply suggestions from code review
  
  Apply Aleksey's suggestions of May 17
  
  Co-authored-by: Aleksey Shipilëv <shipilev at amazon.de>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13815/files
  - new: https://git.openjdk.org/jdk/pull/13815/files/4a486cfd..9023b6c3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13815&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13815&range=02-03

  Stats: 8 lines in 2 files changed: 1 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/13815.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13815/head:pull/13815

PR: https://git.openjdk.org/jdk/pull/13815