Add col integrality helpers

[Opt-Mucca]

This was inspired from a comment by @fwesselm from PR #2671
It is a small refactor that adds some helper functions for determining the variable type of a column.

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.26%. Comparing base (263398e) to head (9fa4d0c).
⚠️ Report is 10 commits behind head on latest.

Files with missing lines	Patch %	Lines
highs/mip/HighsMipSolverData.cpp	50.00%	3 Missing ⚠️
highs/mip/HighsSearch.cpp	60.00%	2 Missing ⚠️
highs/mip/HighsLpRelaxation.cpp	66.66%	1 Missing ⚠️
highs/mip/HighsModkSeparator.cpp	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #2680      +/-   ##
==========================================
- Coverage   81.26%   81.26%   -0.01%     
==========================================
  Files         349      349              
  Lines       85779    85775       -4     
==========================================
- Hits        69707    69703       -4     
  Misses      16072    16072              

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