RFR: 8359707: Add classfile modification code to RedefineClassHelper [v2]

[Serguei Spitsyn]

On Tue, 24 Jun 2025 15:56:49 GMT, Chen Liang <liach at openjdk.org> wrote:

>> I did copy this code.  I was hoping instead of class byte modifications that someone would suggest a Classfile API way to modify the class file bytes. @liach ? That way the class names don't have to be the same length.  Above seems better  code but I have to debug it now.
>
> `jdk.internal.classfile.components` has a `ClassRemapper` that may serve this purpose. It updates all internal names and occurrences in descriptors.

BTW, I've also noticed this issue with returning 0 but forgot to post my question. This suggestion from Alex looks good to me, at least, if the `ClassRemapper` is tricky to borrow.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25857#discussion_r2165816599