Update from_cmdstanpy converter to follow schema convention

[utkarsh-maheshwari]

Description

Matched sample stats according to InferenceData schema specification in from_cmdstanpy converter. Addreses issue #1514

Checklist

• Follows official PR format
• Code style correct (follows pylint and black guidelines)
• Changes are listed in changelog

[codecov]

Codecov Report

Merging #1550 (e520a79) into main (f4606e4) will increase coverage by 0.79%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1550      +/-   ##
==========================================
+ Coverage   90.27%   91.07%   +0.79%     
==========================================
  Files         105      105              
  Lines       11397    11362      -35     
==========================================
+ Hits        10289    10348      +59     
+ Misses       1108     1014      -94     

Impacted Files	Coverage Δ
arviz/data/io_cmdstanpy.py	98.20% <100.00%> (+37.50%)	⬆️
arviz/plots/hdiplot.py	88.13% <0.00%> (-4.32%)	⬇️
arviz/plots/violinplot.py	83.33% <0.00%> (-3.04%)	⬇️
arviz/plots/forestplot.py	91.17% <0.00%> (-2.58%)	⬇️
arviz/plots/posteriorplot.py	87.50% <0.00%> (-2.50%)	⬇️
arviz/utils.py	87.34% <0.00%> (-1.95%)	⬇️
arviz/plots/densityplot.py	88.88% <0.00%> (-1.50%)	⬇️
arviz/stats/stats.py	96.12% <0.00%> (-0.45%)	⬇️
arviz/plots/loopitplot.py	97.72% <0.00%> (ø)
arviz/plots/backends/bokeh/loopitplot.py	94.87% <0.00%> (ø)
... and 4 more

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[OriolAbril]

Hi @utkarsh-maheshwari sorry for the inconvenience, a new cmdstanpy version was released and broke the ci tests, so we merged a fix before merging this PR. You'll now need to rebase/merge the latest changes and most importantly, handle the merge conflicts that arise. Not sure if you have ever handled merge conflicts, if you need help let us know

[OriolAbril]

Note: also fix the links in the first bullet point of changelog.

[utkarsh-maheshwari]

Not sure if you have ever handled merge conflicts, if you need help let us know

Okay, I would like to attempt it first and would seek help if any issue is there. Thanks!

[OriolAbril]

Thanks @utkarsh-maheshwari