L Shaped Standard Optimality Cuts and L1 Feasibility Cuts

[domyang]

This pull request implements a standalone class which generates Benders cuts StandardLPL1CutGenerator. It is distinguished from the current implementation in that it uses traditional Benders optimality cuts as opposed to the blended feasibility/optimality cuts currently used in LShapedCutGeneratorData. It also implements feasibility cuts using L1 Normalization as described in "Implementing Automatic Benders Decomposition in a Modern MIP Solver" (Bonami et al. 2020). This is similar to the current implementation but it excludes the additional constraint derived from the objective.

[codecov]

Codecov Report

❌ Patch coverage is 12.60870% with 201 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.14%. Comparing base (29671ec) to head (35d14de).

Files with missing lines	Patch %	Lines
mpisppy/utils/lshaped_cuts.py	11.21%	198 Missing ⚠️
mpisppy/opt/lshaped.py	57.14%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #835      +/-   ##
==========================================
- Coverage   77.77%   77.14%   -0.63%     
==========================================
  Files         177      177              
  Lines       23764    23992     +228     
==========================================
+ Hits        18482    18509      +27     
- Misses       5282     5483     +201     

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