Implemented 2-epoch demographic model for Vaquita

[igronau]

I implemented the 2-epoch demographic model from Robinson et al. (2022), which is what we plan on using for the simulations in the selection paper (for DFE inference). See #1508

[petrelharp]

Awesome!

I've tried bumping the cache number to get the tests to run?!?!

[petrelharp]

Looks good - one minor wording fix!

[petrelharp]

Closes #1508.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (b185585) 99.85% compared to head (fc42476) 99.85%.
Report is 12 commits behind head on main.

❗ Current head fc42476 differs from pull request most recent head 60d89cc. Consider uploading reports for the commit 60d89cc to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1526   +/-   ##
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  Coverage   99.85%   99.85%           
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  Files         125      126    +1     
  Lines        4217     4228   +11     
  Branches      588      588           
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+ Hits         4211     4222   +11     
  Misses          3        3           
  Partials        3        3           

Files	Coverage Δ
stdpopsim/catalog/PhoSin/__init__.py	100.00% <100.00%> (ø)
stdpopsim/catalog/PhoSin/demographic_models.py	100.00% <100.00%> (ø)

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[petrelharp]

These tests run fine locally for me; I will merge this without CI passing, pending #1529 .

[petrelharp]

Can you open the QC issue, @igronau ?