[WIP] fix containment direction for ANI calculation

[ctb]

Fixes https://github.com/sourmash-bio/sourmash/issues/2193 Fixes https://github.com/sourmash-bio/sourmash/issues/2194

This PR fixes the direction of containment for the ANI calculation, per #2193.

TODO:

• [ ] rename containment_ani to contained_by_as_ani
• [ ] write more tests
• [ ] update compare documentation

[codecov[bot]]

Codecov Report

Merging #2215 (53a8c0f) into latest (536d39d) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           latest    #2215   +/-   ##
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  Coverage   84.66%   84.66%           
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  Files         131      131           
  Lines       15512    15512           
  Branches     2210     2210           
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  Hits        13134    13134           
  Misses       2085     2085           
  Partials      293      293           

Flag	Coverage Δ
python	92.04% <100.00%> (ø)
rust	65.29% <ø> (ø)

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Impacted Files	Coverage Δ
src/sourmash/search.py	97.93% <100.00%> (ø)
src/sourmash/sketchcomparison.py	97.12% <100.00%> (ø)

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[ctb]

so @bluegenes I was struck by the fact that only one test, tests/test_sourmash.py::test_search_ani_containment_estimate_ci, was broken by this fix, and that the actual ANI estimate didn't change, just the CI. It's fantastic that a test broke, but I'd like a clearer example of where this matters ;).

I was thinking that I could write a few more tests - specifically,

• one where the containment ANI is quite asymmetric
• one for the compare matrix to verify the values

If this seems like a bad idea, speak ~now-ish or forever hold your peace :)

[ctb]

ready for review & merge @bluegenes!