Add federal TANF baseline infrastructure for state implementations

[hua7450]

Fixes #6741

[codecov]

Codecov Report

❌ Patch coverage is 94.59459% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.59%. Comparing base (bb9ac27) to head (bdc83a6).
⚠️ Report is 42 commits behind head on master.

Files with missing lines	Patch %	Lines
policyengine_us/variables/gov/hhs/tanf/tanf_fpg.py	90.47%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##            master    #6742      +/-   ##
===========================================
- Coverage   100.00%   94.59%   -5.41%     
===========================================
  Files            1        3       +2     
  Lines           22       37      +15     
  Branches         0        1       +1     
===========================================
+ Hits            22       35      +13     
- Misses           0        1       +1     
- Partials         0        1       +1     

Flag	Coverage Δ
unittests	94.59% <94.59%> (-5.41%)	⬇️

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[PavelMakarchuk]

minor