RFR: 8297301: Cleanup unused methods in JavaUtilJarAccess [v5]

[Weijun Wang]

On Sun, 20 Nov 2022 06:27:32 GMT, pandaapo <duke at openjdk.org> wrote:

>> The cache named `signerToCodeSource` in `JarVerifier` is never used now.
>
> pandaapo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Modify as reviews.

`codomain`, `VerifierCodeSource`, `isSigningRelated`, and `getUnsignedCS` also used nowhere.

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PR: https://git.openjdk.org/jdk/pull/11072