Add icdf function for Cauchy and Logistic distributions

[amyoshino]

What is this PR about?
Adds ICDF functions to

• Cauchy Distribution
• Logistic Distribution

References:
https://en.wikipedia.org/wiki/Logistic_distribution
https://en.wikipedia.org/wiki/Cauchy_distribution

Issue #6612

Checklist

• Explain important implementation details 👆
• Make sure that the pre-commit linting/style checks pass.
• Link relevant issues (preferably in nice commit messages)
• Are the changes covered by tests and docstrings?
• Fill out the short summary sections 👇

Major / Breaking Changes

• ...

New features

• Cauchy.icdf function.
• Logistic.icdf function.

Bugfixes

• ...

Documentation

• ...

Maintenance

• ...

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📚 Documentation preview 📚: https://pymc--6747.org.readthedocs.build/en/6747/

[codecov]

Codecov Report

Merging #6747 (53418bd) into main (154f5b0) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6747   +/-   ##
=======================================
  Coverage   91.89%   91.90%           
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  Files          95       95           
  Lines       16147    16155    +8     
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+ Hits        14839    14847    +8     
  Misses       1308     1308           

Impacted Files	Coverage Δ
pymc/distributions/continuous.py	97.75% <100.00%> (+0.01%)	⬆️

[amyoshino]

Ok, I decided to transform this into a PR for the Cauchy and Logistic distributions only. I will work with LogNormal in a separate PR, posting my findings about the precision issue I'm having with the test.

Apologies for this turnaround, please let me know if anything for Cauchy and Logistic is missing here.

Thanks,

[amyoshino]

I believe this PR is good to go! Let me know if you need me to work on anything with these two functions and tests.

[ricardoV94]

Looks great!