Playing with MQF

[luizirber]

This PR implements a new SBT using MQFs as internal nodes, based on the rust_ffi branch at the MQF repo.

(it was also driving what features to expose initially on the MQF wrapper).

Since there is no index building implemented in Rust yet, https://github.com/dib-lab/sourmash/compare/rust/mqf_sketch?expand=1#diff-7154331bd19ac9d7b71a5499ac5955a8 is building the internal nodes explicitly (and will serve as reference for when index building is actually implemented).

Checklist

• Is it mergeable?
• make test Did it pass the tests?
• make coverage Is the new code covered?
• Did it change the command-line interface? Only additions are allowed
  without a major version increment. Changing file formats also requires a
  major version number increment.
• Was a spellchecker run on the source code and documentation after
  changes were made?

[codecov]

Codecov Report

Merging #772 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #772   +/-   ##
=======================================
  Coverage   89.48%   89.48%           
=======================================
  Files          29       29           
  Lines        4554     4554           
  Branches       46       46           
=======================================
  Hits         4075     4075           
  Misses        476      476           
  Partials        3        3

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[ctb]

...are we bypassing reviews now, or is this a "doesn't actually affect sourmash functionality ATM" merge? :)

[luizirber]

I've been merging rust-only branches, do you want to review them?
(Anything touching Python/Cython/C++ goes thru review, of course)

[luizirber]

I've also trying to bring down my branches/PR count, too much work on keeping everything in sync...