Rewrite verification_mock helpers in Rust

[cpu]

Presently the mock verification test cases are generated using Go

It's likely possible to rewrite these test helpers in Rust, making maintenance a little bit easier. For inspiration, consider a similar rewrite that was done for the Rustls repo test pki where an example generates a modestly complex PKI in pure Rust using rcgen.

Putting this issue in the tracker for a rainy day.

[yerke]

Updated links to mock verification test cases and real world verification test cases.

[cpu]

@yerke Thanks!

I updated this issue to reflect that the real world verification helper script was rewritten in #44. It's just the mock verification test cases that need similar treatment now.

The updated issue description uses permalinks and also provides a link to similar work I did in the upstream rustls repo for inspiration. I'm not planning to tackle this myself anytime soon but hopefully these pointers help whoever decides to take a crack at it.