RFR: 8358483: G1: Remove G1HeapRegionManager::num_available_regions [v2]

[Thomas Schatzl]

On Wed, 11 Jun 2025 14:37:46 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Simple cleanup of moving an API from `G1HeapRegionManager` to `G1CollectedHeap`.
>> 
>> Test: tier1
>
> Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - review
>  - Merge branch 'master' into g1-move-api
>  - g1-move-api

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/25611#pullrequestreview-2920738634