Implement loops v2

[tsmbland]

Description

Fixes #794

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

❌ Patch coverage is 20.26144% with 122 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.30%. Comparing base (f83508c) to head (ae00efc).

Files with missing lines	Patch %	Lines
src/simulation/investment.rs	5.78%	113 Missing and 1 partial ⚠️
src/simulation/optimisation.rs	74.19%	8 Missing ⚠️

Additional details and impacted files

@@                   Coverage Diff                   @@
##           unmet_demand_output     #986      +/-   ##
=======================================================
- Coverage                84.13%   82.30%   -1.83%     
=======================================================
  Files                       52       52              
  Lines                     5804     5929     +125     
  Branches                  5804     5929     +125     
=======================================================
- Hits                      4883     4880       -3     
- Misses                     684      812     +128     
  Partials                   237      237              

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