Low level model refactoring.

[daveshanley]

After years of organic growth, it's time to really tune things up as I prepare the library for a v1 release. There is much to do, lots of cleaning, tuning, polishing, refactoring, and upgrades.

This PR has the low-level models tuned with lookups running faster, and the build paths are more optimized.

No new features, no breaking changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.67%. Comparing base (65096b4) to head (d445f74).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #556      +/-   ##
==========================================
+ Coverage   99.64%   99.67%   +0.03%     
==========================================
  Files         253      260       +7     
  Lines       28302    28625     +323     
==========================================
+ Hits        28202    28533     +331     
+ Misses         61       55       -6     
+ Partials       39       37       -2     

Flag	Coverage Δ
unittests	99.67% <100.00%> (+0.03%)	⬆️

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