RFR: 8356577: Migrate ClassFileVersionTest to be feature-agnostic

[Chen Liang]

On Thu, 8 May 2025 20:05:56 GMT, Chen Liang <liach at openjdk.org> wrote:

> In #24923 we noted that ClassFileVersionTest depends on arbitrary preview features to have javac mark itself as preview. This creates an extra, hard-to-detect dependency on those features, and make its maintenance costly. The best way to have a class that has preview bit is to use ClassFile API to generate such a simple class instead, now that ClassFile API is available.
> 
> Testing: This test itself

Thanks for the reviews!

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PR Comment: https://git.openjdk.org/jdk/pull/25128#issuecomment-2867953140