Classic McEliece Cryptodoc

[FAlbertDev]

Crypto documentation for Botan's Classic McEliece implementation.

Truncated Source Links

I experimented with the :srcref: restructuredText role for this documentation. I think the file location lists are unnecessarily bulked with redundant data. I introduced a truncated :srcref view that addresses this problem. In Classic McEliece, I name the Classic McEliece directory once for the reader and then use something like:
:srcref:`[src/lib/pubkey/classic_mceliece]/cmce_types.h` which is displayed as .../cmce_types.h. The link works properly, of course.

Note that the CI fails until randombit/botan#3883 is merged.

TODO Tracker

• Internal Review
• After FrodoKEM Cryptodoc #117 and HSS/LMS Crypto Documentation #140 are merged: Update the source file name numbers and sort the new chapter into the document.

[reneme]

Re:sourceref: I'll have a go at the discussion we had in the FrodoKEM PR. Let's see how we can integrate this. But having an explicit way to shorten the reference links is certainly a good idea.

Edit: I cherry-picked your path elision feature in #188. Let's rebase once that is merged.

[reneme]

Rebased to main, resolved pending merge conflicts and removed the commit adding the truncation feature to :srcref:. This now uses the unified :srcref: extensions that came in #188.

[atreiber94]

Very nice, I like it a lot! I added some editorial comments

[FAlbertDev]

Thanks for your comprehensive review, @atreiber94! I addressed your comments.

[atreiber94]

Thanks, lgtm!

I left open some minor things, most notably I think we should explicitly rule out introducing timing side channels by utilizing the bitvector class when we mention that only parts of the functionality are constant time.

[atreiber94]

Addressed all the comments