RFR: 8371667: Shenandoah: Re-design alloc request type enum for better efficiency and cleaner code [v12]

[Xiaolong Peng]

On Mon, 17 Nov 2025 16:32:35 GMT, Xiaolong Peng <xpeng at openjdk.org> wrote:

>> Xiaolong Peng has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Adding unnecessary back
>
> src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp line 1618:
> 
>> 1616:   size_t ac = alloc_capacity(r);
>> 1617:   ShenandoahFreeSetPartitionId orig_partition;
>> 1618:   ShenandoahGeneration* request_generation = nullptr;
> 
> `ac` and `request_generation` are not actually used, we can remove them, but it is not really related to the purpose of this PR, probably better create a separate PR for the clean-ups.

Reverted the unnecessary change for `ac` and `request_generation`

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PR Review Comment: https://git.openjdk.org/jdk/pull/28247#discussion_r2534788166