Fix 3221

[filikat]

Description

• Substitute hard coded value of 64 for cache line size with a constant kCacheLineSize, so that it is easier to modify it and recompile Highs on a machine with different cache line size.
• Update the "ToDo" comment in HighsSpinMutex to highlight that std::this_thread::yield() is the correct instruction to use on AArch64.

Checklist

• I have read the contributing guidelines
• This PR targets the latest branch
• Tests are passing
• Documentation was updated where relevant
• This PR is not primarily AI-generated (per the AI contributions policy in CONTRIBUTING.md)

Related issue

Closes #3221

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.57%. Comparing base (b440ef0) to head (c3aee6e).
⚠️ Report is 105 commits behind head on latest.

Files with missing lines	Patch %	Lines
highs/parallel/HighsSplitDeque.h	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3281      +/-   ##
==========================================
+ Coverage   73.31%   73.57%   +0.26%     
==========================================
  Files         446      446              
  Lines      108299   109532    +1233     
  Branches    17347    17547     +200     
==========================================
+ Hits        79396    80592    +1196     
- Misses      28627    28663      +36     
- Partials      276      277       +1     

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[mathgeekcoder]

Looks good! Minor suggestions if you wanted some improvements.

[mathgeekcoder]

Looks good!