RFR: 8367759: G1: Move G1UpdateRegionLivenessAndSelectForRebuildTask into its own file

[Albert Mingkun Yang]

On Tue, 16 Sep 2025 14:19:41 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change to move `G1UpdateRegionLivenessAndSelectForRebuildTask` into a separate file. I would like to merge this class and G1BuildCandidateRegionsTask in the near future because the latter mostly repeats the work of the former anyway, but together (with helper classes) they are quite large (if not large already by themselves). This should help make `g1ConcurrentMark.cpp` a little more manageable.
> 
> There is no change in the code, just moving and fixing includes/adding forwards.
> 
> Testing: local compilation, gha
> 
> Thanks,
>   Thomas

Marked as reviewed by ayang (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27314#pullrequestreview-3243598419