WIP: Add keyed blake2

[srasoamiaramanana-ledger]

Description

This PR enables the use of Blake2b with a key, a salt or a personalization string in a 'all in one' way.

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

Breaking changes

Additional comments

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.42%. Comparing base (276361f) to head (8e49c3a).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #547   +/-   ##
=======================================
  Coverage   60.42%   60.42%           
=======================================
  Files          12       12           
  Lines        1660     1660           
=======================================
  Hits         1003     1003           
  Misses        657      657           

Flag	Coverage Δ
unittests	60.42% <ø> (ø)

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