New optimization algorithms

[bwohlberg]

Add linearized ADMM and PDHG optimization algorithms.

See also lanl/scico-data#7.

[codecov]

Codecov Report

Merging #117 (82a96ea) into main (50e4935) will increase coverage by 0.37%.
The diff coverage is 98.15%.

@@            Coverage Diff             @@
##             main     #117      +/-   ##
==========================================
+ Coverage   90.89%   91.26%   +0.37%     
==========================================
  Files          42       44       +2     
  Lines        2997     3160     +163     
==========================================
+ Hits         2724     2884     +160     
- Misses        273      276       +3     

Flag	Coverage Δ
unittests	91.26% <98.15%> (+0.37%)	⬆️

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Impacted Files	Coverage Δ
scico/ladmm.py	97.67% <97.67%> (ø)
scico/primaldual.py	98.70% <98.70%> (ø)

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[Michael-T-McCann]

"style police" comments are FYI rather than blockers, I can tidy them up later if you wish.