Unit tests for AMM offer overflow fix

[Bronek]

High Level Overview of Change

Unit tests for #4968

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

[gregtatcam]

Does it make sense to add expected offer balances? This way we can see the amounts going via AMM/LOB.

[ckeshava]

@gregtatcam I agree, please view it here: Bronek#1

Qualitatively, the LOB offers are being used when one side of the AMM is being overwhelmed by sendmax parameter. This makes sense because LOB provides better quality offers whereas the AMM becomes capital-inefficient towards extremities.

However, I'm not familiar enough with the synthetic offer generation process to validate the actual numbers myself. Let me know if I can improve the validation further.

[scottschurr]

This test looks good to me as it is. If you want to enhance it, I'm good with that too.

[gregtatcam]

LGTM

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 72.05882% with 19 lines in your changes are missing coverage. Please review.

Project coverage is 76.98%. Comparing base (659bd99) to head (34ff8e7).

Files	Patch %	Lines
src/test/app/AMM_test.cpp	72.05%	18 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4986      +/-   ##
===========================================
+ Coverage    76.97%   76.98%   +0.01%     
===========================================
  Files         1129     1129              
  Lines       131958   132026      +68     
  Branches     39576    39604      +28     
===========================================
+ Hits        101570   101639      +69     
- Misses       24423    24447      +24     
+ Partials      5965     5940      -25     

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