Presolve infrastructure for adding rows/columns

[fwesselm]

• This is just the infrastructure part from Fourier-Motzkin presolve #3191.
• ImpliedEquation reduction type was added to properly handle conversion of inequality constraints into equality constraints.
• Benchmarking (on 100 MIPs) did not reveal any unintended side effects.
• Added a test to exercise new code.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.13%. Comparing base (2ed99be) to head (9bee4bb).
⚠️ Report is 23 commits behind head on latest.

Files with missing lines	Patch %	Lines
highs/presolve/HighsPostsolveStack.cpp	81.31%	17 Missing ⚠️
highs/presolve/HPresolve.cpp	89.15%	9 Missing ⚠️
highs/presolve/HighsPostsolveStack.h	93.24%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3218      +/-   ##
==========================================
+ Coverage   73.06%   73.13%   +0.07%     
==========================================
  Files         445      445              
  Lines      107661   107796     +135     
  Branches    17257    17260       +3     
==========================================
+ Hits        78659    78835     +176     
+ Misses      28726    28685      -41     
  Partials      276      276              

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[Opt-Mucca]

I am a hugeeeeeeeeeeeeeeeeee fan of this PR!!!!! It somehow doesn't complicate the code at all, and even does a latent TODO for equation upgrades!

I've only found two potential issues. Both could be me missing the larger picture (not unlikely), but I think they're potential bugs.