RFR: 8306324: StopThread results in thread being marked as interrupted, leading to unexpected InterruptedException

[Serguei Spitsyn]

If JVMTI `StopThread` is done when the thread is in certain various states (but not all states), after the `async` exception is delivered and handled, hotspot leaves the thread's `interrupted` flag set. The end result is the next time the thread does something like `Thread.sleep()`, it will immediately get an `InterruptedException`.

The fix is to clear the `interrupted` flag in the `JavaThread::handle_async_exception()` after an `async` pending exception has been set to be thrown with the `set_pending_exception()`.

There are a couple of concerns with this fix which would be nice to sort out with reviewers:
1.  The proposed fix may clear the interrupt state when it was already set prior to the issuing of the `StopThread()` (this concern was raised by @dholmes-ora in a comment of this JBS issue)
2.  The impacted code path is shared between the class `InstallAsyncExceptionHandshakeClosure` used by the JVMTI `StopThread` implementation and the class `ScopedAsyncExceptionHandshakeClosure` used by the `ScopedMemoryAccess`

I feel that clearing the `interrupted` flag byt the `JavaThread::handle_async_exception()` is a right thing to do even though it was set before the call to `JavaThread::install_async_exception()`. Also, it has to be done for both `StopThread` and `ScopedMemoryAccess`.

The fix also includes minor tweaks of the test `StopThreadTest` to make the issue reproducible with it.

Testing:
 - Mach5 tiers 1-6 are passed
 - Ran the updated reproducer test `hotspot/jtreg/serviceability/jvmti/vthread/StopThreadTest`

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Commit messages:
 - 8306324: StopThread results in thread being marked as interrupted, leading to unexpected InterruptedException

Changes: https://git.openjdk.org/jdk/pull/26365/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26365&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306324
  Stats: 7 lines in 2 files changed: 4 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26365.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26365/head:pull/26365

PR: https://git.openjdk.org/jdk/pull/26365