RFR: 8249004: Reduce ThreadListHandle overhead in relation to direct handshakes [v2]

[Daniel D.Daugherty]

> A trivial fix to reduce ThreadListHandle overhead in relation to handshakes.
> 
> This refactoring was tested with Mach5 Tier[1-3].

Daniel D. Daugherty has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into JDK-8249004
 - 8249004: Reduce ThreadListHandle overhead in relation to direct handshakes

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4677/files
  - new: https://git.openjdk.java.net/jdk/pull/4677/files/8162b22f..bc82cfa6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4677&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4677&range=00-01

  Stats: 38422 lines in 1014 files changed: 17121 ins; 15900 del; 5401 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4677.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4677/head:pull/4677

PR: https://git.openjdk.java.net/jdk/pull/4677