RFR: 8262454: Handshake timeout improvements, single target, kill unfinished thread [v4]

[Robbin Ehn]

> When executing a single target handshake we do not have a timeout.
> When we timeout we should crash the thread with the non-completed handshake operation.
> 
> VM_Handshake only had one implementer so I remove it.
> 
> Passes t1-5.

Robbin Ehn 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 eight additional commits since the last revision:

 - Merge branch 'master' into 8262454-hs-timeout-st
 - Added comment, sorted imports in test
 - Spelling error
 - Fixed cr year
 - Merge branch 'master' into 8262454-hs-timeout-st
 - Use WB waitUnsafe to trigger timeout
 - Merge branch 'master' into 8262454-hs-timeout-st
 - Fixed timeout

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2743/files
  - new: https://git.openjdk.java.net/jdk/pull/2743/files/c218c226..e6585f93

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2743&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2743&range=02-03

  Stats: 2047 lines in 113 files changed: 1058 ins; 243 del; 746 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2743.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2743/head:pull/2743

PR: https://git.openjdk.java.net/jdk/pull/2743