RFR: 8320969: Shenandoah: Enforce stable number of GC workers [v2]

[Y. Srinivas Ramakrishna]

On Wed, 6 Dec 2023 14:16:49 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> See bug for rationale.
>> 
>> Additional testing:
>>  - [x] MacOS AArch64 server fastdebug, `hotspot_gc_shenandoah`
>>  - [x] Linux x86_64 server fastdebug, `tier{1,2,3}` with `-XX:+UseShenandoahGC`
>>  - [x] Linux AArch64 server fastdebug, `tier{1,2,3}` with `-XX:+UseShenandoahGC`
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8320969-shenandoah-stable-gc-workers
>  - Reinstate the .cpp policy code
>  - Merge branch 'master' into JDK-8320969-shenandoah-stable-gc-workers
>  - No dynamic GC workers

Reviewed!

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Marked as reviewed by ysr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16878#pullrequestreview-1768551188