Hierarchical stat growthss

[joshqsumner]

extending stat_growthss to use hierarchical models

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.62%. Comparing base (632de91) to head (6af3384).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #166      +/-   ##
==========================================
- Coverage   99.66%   99.62%   -0.05%     
==========================================
  Files          83       83              
  Lines        8696     8700       +4     
==========================================
  Hits         8667     8667              
- Misses         29       33       +4     

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