RFR: 8286830: ~HandshakeState should not touch oops

[Patricio Chilano Mateo]

On 8284632 we added ~HandshakeState to cleanup any potential async operations left in the handshake queue. This could trigger the release of an oophandle from its associated oop-storage when trying to delete an AsyncExceptionHandshake object. Since the exiting JT already executed on_thread_detach() this is forbidden. 
To fix this I used the original approach that @dcubed-ojdk posted on the 8284632 fix, which is cleaning up those operations before on_thread_detach() is executed. To make sure that no other async exception operation is added to the queue after that I did two things:
- Added a check in install_async_exception() to avoid installing the operation if the target already moved to the _thread_exiting state.
- Move the setting of the _thread_exiting state to include the case where JavaThread::exit() is called with destroy_vm=true.

I also added another run to tests StopAtExit.java and SuspendAtExit.java with extra contention on the Threads_lock. That increases the odds of the target being handshake safe while being in the _thread_exiting state which allows testing for more pathological cases.

I was able to reproduce the issue by running StopAtExit.java with -XX:+UseShenandoahGC and verified that the test now passes. I also run mach5 tiers1-3. Will run the upper tiers also and will do an additional pass after that.

Thanks,
Patricio

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Commit messages:
 - v1

Changes: https://git.openjdk.java.net/jdk/pull/8795/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8795&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286830
  Stats: 84 lines in 5 files changed: 73 ins; 8 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8795.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8795/head:pull/8795

PR: https://git.openjdk.java.net/jdk/pull/8795