DOC: Add rcParams defaults and descriptions to documentation (#2457)

[pranavkp71]

This PR adds a complete table of all ArviZ rcParams, including their default
values and short descriptions, based on the definitions in arvizrc.template.

This improves the documentation page at rcParams by listing all available
configuration keys in a clear and accessible way.

Fixes #2457.

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📚 Documentation preview 📚: https://arviz--2496.org.readthedocs.build/en/2496/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.81%. Comparing base (4db6129) to head (2e0df90).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2496      +/-   ##
==========================================
- Coverage   86.84%   86.81%   -0.04%     
==========================================
  Files         124      124              
  Lines       13036    13036              
==========================================
- Hits        11321    11317       -4     
- Misses       1715     1719       +4     

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[pranavkp71]

Hi @OriolAbril and @williambdean,

I think the failing tests are unrelated to this docs-only change.
BaseTests and the documentation build succeeded.

If anything is needed from my side, please let me know. Thanks

[OriolAbril]

Hi, sorry we need to go over all the issues and either comment they should now apply to one of arviz-base, arviz-stats or arviz-plots or close them. A large number of issues have actually been solved already as part of the refactor (like this one, arviz-base does document all rcParams explicitly). I will have to close this as we only plan to merge critical improvements to arviz 0.x (which best case scenario will be none). Definitely let us know if you are interested in helping out with the documentation around the refactor!