Simplified factorisation for HiPO

[filikat]

• Add up-looking factorisation. This is a simplified sparse factorisation that works well when the matrix is very sparse.
• Add criterion to select whether to use the up-looking factorisation or the multi-frontal one.
• Add option hipo_factor to force the choice of a specific factorisation.
• Add possibility of switching between the two factorisations. This is used mainly if the up-looking factorisation (which is slightly less robust for now) fails, to continue iterating using the multi-frontal one
• If HiPO fails, it resets to the best iteration that it found before switching to IPX or switching factorisation.
• Changed the way HiPO manages the status of the solve process, keeping track of errors separately from the status.
• Removed unnecessary memory allocations and swaps from the triangular solves, as suggested by Claude/hipo parallel solve sketch #3152.
• Changed the internal time profiling.
• Removed a lot of useless comments, unused functions, and improved general readability of the code.

[codecov]

Codecov Report

❌ Patch coverage is 0.74503% with 1199 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.92%. Comparing base (2709311) to head (159714e).
⚠️ Report is 175 commits behind head on latest.

Files with missing lines	Patch %	Lines
highs/ipm/hipo/ipm/Solver.cpp	0.00%	313 Missing ⚠️
highs/ipm/hipo/ipm/UpLookingSolver.cpp	0.00%	169 Missing ⚠️
highs/ipm/hipo/factorhighs/HybridSolveHandler.cpp	0.00%	113 Missing ⚠️
highs/ipm/hipo/ipm/FactorHighsSolver.cpp	0.00%	109 Missing ⚠️
highs/ipm/hipo/factorhighs/FactorHighs.cpp	0.00%	93 Missing ⚠️
highs/ipm/hipo/ipm/Iterate.cpp	0.00%	54 Missing ⚠️
highs/ipm/hipo/factorhighs/Numeric.cpp	0.00%	51 Missing ⚠️
highs/ipm/hipo/factorhighs/FactorHighs_c_api.cpp	0.00%	47 Missing ⚠️
highs/ipm/hipo/factorhighs/DenseFactKernel.cpp	0.00%	33 Missing ⚠️
highs/ipm/hipo/ipm/Model.cpp	0.00%	29 Missing ⚠️
... and 25 more

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3159      +/-   ##
==========================================
- Coverage   73.17%   72.92%   -0.25%     
==========================================
  Files         430      436       +6     
  Lines      103967   105843    +1876     
  Branches    16718    17034     +316     
==========================================
+ Hits        76076    77189    +1113     
- Misses      27615    28378     +763     
  Partials      276      276              

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[jajhall]

Fine by me