test: add test hook to corrupt share index

[elliedavidson]

closes: #XXXX

This PR:

This PR adds a small testing function to corrupt VID share indices. The purpose of this function is to create VID shares that fail verify_share with an Ok(Err) result. This PR doesn't need to be merged - it is just to show the bug that was fixed in HotShot. It probably makes sense to instead write logic that returns any form of a corrupt share, instead of writing to specifically corrupt the index of the share.

This PR does not:

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• [x] Linked to GitHub issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• [ ] Wrote unit tests
• [ ] Updated relevant documentation in the code
• [ ] Added relevant changelog entries to the CHANGELOG.md of touched crates.
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[ggutoski]

Thanks @elliedavidson ! Is there a reason not to merge this PR?

Sucks that you need to touch the VidScheme trait. That could probably be avoided by setting the share index to u32::MAX or whatever so you don't need self.num_storage_nodes. But that might not be worth the trouble.

[elliedavidson]

Thanks @elliedavidson ! Is there a reason not to merge this PR?

Sucks that you need to touch the VidScheme trait. That could probably be avoided by setting the share index to u32::MAX or whatever so you don't need self.num_storage_nodes. But that might not be worth the trouble.

Let me try moving it out of VID Scheme!