RFR: 8306034: add support of virtual threads to JVMTI StopThread [v8]

[Serguei Spitsyn]

> This enhancement adds support of virtual threads to the JVMTI `StopThread` function.
> In preview releases before this enhancement the StopThread returned the JVMTI_ERROR_UNSUPPORTED_OPERATION error code for virtual threads.
> 
> The `StopThread` supports sending an asynchronous exception to a virtual thread only if it is current or suspended at mounted state. For instance, a virtual thread can be suspended at a JVMTI event. If the virtual thread is not suspended and is not current then the `JVMTI_ERROR_THREAD_NOT_SUSPENDED` error code is returned. If the virtual thread was suspended at unmounted state then the `JVMTI_ERROR_OPAQUE_FRAME` error code is returned.
> 
> The `StopThread` has the following description for `JVMTI_ERROR_OPAQUE_FRAME` error code:
>> The thread is a suspended virtual thread and the implementation 
>> was unable to throw an asynchronous exception from this frame.
> 
> A couple of the `serviceability/jvmti/vthread` tests has been updated to adopt to new `StopThread` behavior.
> 
> The CSR is: https://bugs.openjdk.org/browse/JDK-8306434
> 
> Testing:
> The mach5 tears 1-6 are in progress.
> Preliminary test runs were good in general.
> The JDB test `vmTestbase/nsk/jdb/kill/kill001/kill001.java` has been problem-listed and will be fixed by the corresponding debugger enhancement which is going to adopt JDWP/JDI specs to new behavior of the JVMTI `StopThread` related to virtual threads.
> 
> Also, two JCK JVMTI tests are failing in the tier-6 :
>> vm/jvmti/StopThread/stop001/stop00103/stop00103.html
>> vm/jvmti/StopThread/stop001/stop00103/stop00103a.html
> 
> These two tests will be excluded from the test runs by the JCK team and then adjusted to new `StopThread` behavior.

Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:

  minor tweak of JVMTI_ERROR_OPAQUE_FRAME description

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13546/files
  - new: https://git.openjdk.org/jdk/pull/13546/files/50e615eb..0ad9a6cc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13546&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13546&range=06-07

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13546.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13546/head:pull/13546

PR: https://git.openjdk.org/jdk/pull/13546