RFR: 8357995: Use "stdin.encoding" for reading System.in with InputStreamReader/Scanner [core] [v6]

[Naoto Sato]

On Wed, 11 Jun 2025 10:43:47 GMT, Volkan Yazici <vyazici at openjdk.org> wrote:

>> Passes the `Charset` read from the `stdin.encoding` system property while creating `InputStreamReader` or `Scanner` instances for `System.in`.
>> 
>> `stdin.encoding` is a recently added property for Java 25 in [JDK-8350703](https://bugs.openjdk.org/browse/JDK-8350703). Employing it throughout the entire code base is addressed by the parent ticket [JDK-8356893](https://bugs.openjdk.org/browse/JDK-8356893). JDK-8357995 this PR is addressing is a sub-task of JDK-8356893 and is concerned with only areas related to core libraries.
>
> Volkan Yazici has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revert superfluous test changes

LGTM

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Marked as reviewed by naoto (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25544#pullrequestreview-2922513387