Add timeout support for IIS search

[haman80]

Add timeout support to getIIS

• Introduced a new iis_time_limit option to distinguish IIS search limits from the time_limit option
• Updated deletion filtering to return a partial IIS when the time limit is reached
• Added new model status kIisModelStatusTimeLimit

Improve handling of unexpected model statuses

• Temporarily modify options that may interfere with IIS search, including: simplex_iteration_limit, objective_bound, allow_unbounded_or_infeasible, Callbacks
• Updated getIisInterface to first establish infeasibility prior to elastic filtering or deletion filtering; abort IIS computation if the model is not confirmed infeasible
• After confirming infeasibility, attempt elastic filtering if requested; if it fails due to an unknown status, fall back to deletion filtering over the full set of row and column bounds
• Enhanced deletion filtering to skip bounds whose removal results in an unknown model status and return a partial IIS if possible

Enhancements to HighsIis

• Extended HighsIisInfo to track min, max, and mean iteration counts and LP solve times
• Centralize responsibility for updating these metrics
• Added helper methods determineBoundStatus, and processBoundRelaxation to reduce duplicated logic and improve maintainability

[jajhall]

@haman80 I've cleared the merge conflicts and pushed to Git

[codecov]

Codecov Report

❌ Patch coverage is 84.21053% with 45 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.66%. Comparing base (f6ef98a) to head (994948f).
⚠️ Report is 15 commits behind head on latest.

Files with missing lines	Patch %	Lines
highs/lp_data/HighsInterface.cpp	75.00%	34 Missing ⚠️
highs/lp_data/HighsIis.cpp	88.23%	10 Missing ⚠️
highs/lp_data/HighsOptions.h	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #2870      +/-   ##
==========================================
+ Coverage   80.37%   80.66%   +0.28%     
==========================================
  Files         348      348              
  Lines       86598    86795     +197     
==========================================
+ Hits        69607    70012     +405     
+ Misses      16991    16783     -208     

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[haman80]

Hi @jajhall ,
Apologies for the additional commits. I added some unit tests to improve coverage, including a couple of new infeasible LP instances (cplex1 and vol1). The vol1 case was initially exhibiting inconsistent behavior across machines due to ill conditioning, which required some iteration to stabilize. I look forward to hearing your thoughts.