RFR: 8347840: Fix testlibrary compilation warnings [v3]

[Leonid Mesnik]

On Thu, 16 Jan 2025 18:14:39 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> There few compiler warning disabled in the testlibary build.
>> They should be fixed or localized and removed from build to prevent new possible issues.
>> 
>> The main goal is to avoid new such issues in the testlibrary. 
>> Tested with tier1-5 to ensure that all tests were passed.
>
> Leonid Mesnik has updated the pull request incrementally with one additional commit since the last revision:
> 
>   revert change

See answer and updated vewrsion.

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PR Review: https://git.openjdk.org/jdk/pull/23143#pullrequestreview-2556833136