Support Ipopt >= 3.13

[jslee02]

Fixes #1504

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• Document new methods and classes
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[codecov]

Codecov Report

Merging #1506 into release-6.9 will decrease coverage by 0.01%.
The diff coverage is 70.96%.

@@               Coverage Diff               @@
##           release-6.9    #1506      +/-   ##
===============================================
- Coverage        57.03%   57.02%   -0.02%     
===============================================
  Files              366      366              
  Lines            27147    27145       -2     
===============================================
- Hits             15484    15479       -5     
- Misses           11663    11666       +3     

Impacted Files	Coverage Δ
dart/optimizer/ipopt/IpoptSolver.cpp	74.10% <70.96%> (-0.37%)	⬇️
dart/dynamics/Skeleton.cpp	65.97% <0.00%> (-0.17%)	⬇️