RFR: 8356455: ZGC: Replace ZIntrusiveRBTree with IntrusiveRBTree [v2]

[Erik Österlund]

On Thu, 8 May 2025 13:01:07 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> [JDK-8350441](https://bugs.openjdk.org/browse/JDK-8350441) was implemented before IntrusiveRBTree was introduced, and as such implemented its own intrusive red-black tree. Now that a shared data structure implementation is available, use that instead.
>> 
>> The switch is straight forward, and the O(1) left and right most node lookup which ZIntrusiveRBTree implements that IntrusiveRBTree does not is trivial to implement on top of the tree.
>> 
>> Initial performance evaluation shows no difference between the two implementations. And the functional testing passes.
>> 
>> Tested Oracle Supported platforms, Oracle tier1-8 ZGC testing tasks.
>
> Axel Boldt-Christmas has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Use private inheritance
>  - Separate tree logic to own class

Marked as reviewed by eosterlund (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/25112#pullrequestreview-2834716108