RFR: 6587699: Document DigestInputStream behavior when skip() or mark() / reset() is used [v3]

[Weijun Wang]

On Thu, 28 Jul 2022 22:45:34 GMT, Weijun Wang <weijun at openjdk.org> wrote:

>> Add an `@implNote` to clarify the behavior when these methods are called. A new test is added.
>
> Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   rewording

CSR is filed at https://bugs.openjdk.org/browse/JDK-8291516, please also take a review.

BTW, I assume there is no need for a release note.

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PR: https://git.openjdk.org/jdk/pull/9667