RFR: 8356455: ZGC: Replace ZIntrusiveRBTree with IntrusiveRBTree

[Erik Österlund]

On Thu, 8 May 2025 05:21:20 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.

Looks good.

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Marked as reviewed by eosterlund (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25112#pullrequestreview-2824168024