add getter functions in solve_problems

[MaxenceGollier]

@tmigot, @amontoison, @dpo

This is safer, it allows to run this with more general subtypes of AbstractNLPModels.
@dpo, this allows to use the benchmarks for AbstractRegularizedNLPModels.

Can one of you review when you have some time ?
I'd need a release afterwards. Thank you!

[Copilot]

Pull request overview

This PR replaces direct field access on AbstractNLPModel instances with getter functions from the NLPModels package in solve_problems. This makes the function compatible with more general subtypes of AbstractNLPModels (such as AbstractRegularizedNLPModels) that may not expose the same internal field structure.

Changes:

• Replaced problem.meta.name, problem.meta.nvar, problem.meta.ncon with get_name(problem), get_nvar(problem), get_ncon(problem) for problem info gathering.
• Replaced direct counter field access (problem.counters.counters / problem.counters) with dynamic getter function calls via getfield(NLPModels, f)(problem) for both regular and NLS counters.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.19%. Comparing base (4c0fcd2) to head (129bb64).
⚠️ Report is 36 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #197      +/-   ##
==========================================
+ Coverage   76.71%   86.19%   +9.48%     
==========================================
  Files          12       10       -2     
  Lines         292      297       +5     
==========================================
+ Hits          224      256      +32     
+ Misses         68       41      -27     

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[MaxenceGollier]

@dpo, again, this one is not on me, it looks like it has been a while since the Documentation workflow and Examples are failing... I think I will end up fixing the workflows of all JSO repos..