Extending limited history to properly check for the existence of past values

[kevinlewi]

In general, this change improves the security properties that are supposed to be attained from a limited history proof. A (full) key history proof provides a list of all past versions for a query key. A limited history proof allows for some past version to be left out of the proof. Previously, the way this was implemented was to literally truncate the older versions.

Now, we are instead properly adding the existence proofs for past marker versions and non-existence proofs for future marker versions.

Specifically in this change, it:

• Removes HistoryParams::SinceEpoch, since this is not really supportable by the existing construction. The only way for specifying a non-default parameter now is with HistoryParams::MostRecent.
• Parameters in the HistoryProof struct were repurposed and renamed to support past and future marker versions
• Added a new get_marker_versions() utility function which determines the past and future version numbers to check as part of the history proof generation and verification
• Moved HistoryParams out from akd and into akd_core since it is also used by verification
• Added a new InvalidVersion error type
• Added tests for the new history proof verification behavior, and updated docs as well

I am also bumping the version to 0.12.0-pre.1, since the introduced changes are incompatible with the previous version.

[codecov-commenter]

Codecov Report

Attention: 16 lines in your changes are missing coverage. Please review.

Comparison is base (24b11de) 87.99% compared to head (939ca72) 88.13%.

Files	Patch %	Lines
akd_core/src/verify/history.rs	92.10%	9 Missing ⚠️
akd/src/directory.rs	87.17%	5 Missing ⚠️
akd/src/errors.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #422      +/-   ##
==========================================
+ Coverage   87.99%   88.13%   +0.13%     
==========================================
  Files          39       39              
  Lines        9054     9200     +146     
==========================================
+ Hits         7967     8108     +141     
- Misses       1087     1092       +5     

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