upki: add binary index to improve performance

[djc]

No description provided.

[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks

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_{Comparing index (37c0f1f) with main (7460f0d)}

[djc]

So apparently this doesn't actually improve performance in revocation-check? Codspeed has it unchanged (but mentions it is ignoring time spent in syscalls, which might be problematic for this). Criterion locally assesses it as a ~7% regression, which I'm assuming includes time spent in syscalls?

[ctz]

I think this looks good in substance and structure, just would like to understand the performance element more.

[djc]

I did more work on this. It is now ~5% faster than the main branch in my testing on macOS. That still feels a little underwhelming but I tried a bunch of further optimizations and didn't find anything with substantial impact.

About 60% of the time in Index::check() is spent on deserializing CRLiteClubcard, so it probably makes sense to focus on the new encoding instead.