RFR: 8296323: JVMTI can_support_virtual_threads not available for agents loaded into running VM [v2]

[Serguei Spitsyn]

On Sat, 19 Nov 2022 07:19:16 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> The can_support_virtual_thread was initially implemented as an onload capability.
>> It is why this capability does not work for the agents loaded into running VM.
>> The fix is to move it from `onload` to `always`capabilities list.
>> 
>> Testing:
>> New test is added: VirtualStartThreadTest.
>> TBD: mach5 jvmti, jdi and tier1-6 tests.
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   roll back unintended VirtualThread.java file update

Thank you for looking at it, Alan.
These late binding agent related issues were surprising for me too.
We missed to add the relevant test coverage.
I'll update the test to add the onload execution mode.

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PR: https://git.openjdk.org/jdk/pull/11246