RFR: 8369420: Parallel: Use multiple workers for class unloading [v3]

[Albert Mingkun Yang]

On Wed, 8 Oct 2025 14:38:44 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Support parallel class unloading in ParallelGC. Much inspiration taken from `G1ParallelCleaningTask`.
>> 
>> Test: tier1-5
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review

Thanks for review.

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PR Comment: https://git.openjdk.org/jdk/pull/27689#issuecomment-3387249443