RFR: 8359119: Change Charset to use StableValue [v3]

[Alan Bateman]

On Tue, 5 Aug 2025 09:08:47 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> Fields and methods can better leverage the Stable Value API compared to using DCL and holder classes. There are also some fields that can be marked `@Stable`.
>> 
>> This PR passes tier1, tier2, and tier3 tests on multiple platforms.
>
> Per Minborg 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 six additional commits since the last revision:
> 
>  - Address comments in PR
>  - Merge branch 'master' into stablify-charset
>  - Revert for loop
>  - Revert more
>  - Revert changes
>  - Add stable value functionality

Marked as reviewed by alanb (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/25727#pullrequestreview-3116665856