RFR: 8368989: Use NMethodMarkingScope and ThreadsClaimTokenScope in shenandoahSTWMark

[Francesco Andreuzzi]

On Wed, 1 Oct 2025 09:19:35 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Replace `StrongRootsScope` with `ThreadsClaimTokenScope` in `shenandoahSTWMark` to be more precise with what is needed and why. 
>> 
>> - `ShenandoahSTWMark` uses `MarkingNMethodClosure`, so we also need `NMethodMarkingScope`.
>> - `nworkers` is guaranteed to be > 0
>> 
>> Passes `tier1` and `tier2` (fastdebug).
>
> Marked as reviewed by ayang (Reviewer).

Thanks for the review @albertnetymk and @shipilev.

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

PR Comment: https://git.openjdk.org/jdk/pull/27589#issuecomment-3359876182