Added ICDF for the discrete uniform distribution.

[gokuld]

What is this PR about?
Adding ICDF functions for the existing discrete uniform distribution.
Issue: 6612
Creation of tests for added ICDF functions.

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

• ICDF function for the discrete uniform distribution.

Bugfixes

• ...

Documentation

• ...

Maintenance

• Extended test_discrete.py with corresponding tests.

[codecov]

Codecov Report

Merging #6617 (bead510) into main (067d89b) will decrease coverage by 4.92%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6617      +/-   ##
==========================================
- Coverage   92.01%   87.10%   -4.92%     
==========================================
  Files          93       93              
  Lines       15742    15746       +4     
==========================================
- Hits        14485    13715     -770     
- Misses       1257     2031     +774     

Impacted Files	Coverage Δ
pymc/distributions/discrete.py	98.73% <100.00%> (+0.01%)	⬆️

... and 16 files with indirect coverage changes

[ricardoV94]

Looks good!

[ricardoV94]

Thanks @gokuld!

[gokuld]

@ricardoV94 Thank you!