RFR: 8356107: [java.lang] Use @requires tag instead of exiting based on os.name or separatorChar property

[Naoto Sato]

On Fri, 9 May 2025 23:23:27 GMT, Brent Christian <bchristi at openjdk.org> wrote:

> For `java.lang` tests, use the `@requires` facility in place of checking the `os.name` system property or `File.separatorChar`.
> 
> Automated test results are omitted as expected.

I think `test/jdk/java/lang/System/NonAnsiFileEncodingTest.java` can be removed, as it does not provide any value today :-
- It intends to run on Windows 2000/XP, which are both no longer supported.
- The test requires manual set up to one of those locales on Windows.
- `file.encoding` is always UTF-8 since JDK 18. (and it is actually comparing it with "utf-8" in case-insensitive way)

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PR Review: https://git.openjdk.org/jdk/pull/25163#pullrequestreview-2829970870