RFR: 8364925: G1: Improve program flow around incremental collection set building [v2]

[Albert Mingkun Yang]

On Thu, 7 Aug 2025 15:15:08 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   please review this change that improves the G1CollectionSet incremental state handling slightly:
>> 
>> * remove `_selected_groups_cur_length` with getter as we do not need a copy of that value around
>> * move implementations of some methods from header files into cpp file
>> * moved some incremental state updates from `finalize_old_part` to the respective `start/continue/stop_incremental_building` method
>> 
>> Testing: gha
>> 
>> Thanks,
>>   Thomas
>
> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
> 
>   * ayang review

Marked as reviewed by ayang (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/26659#pullrequestreview-3097620130