Add faster NegativeBinomial

[aloctavodia]

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.55556% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 83.14%. Comparing base (32fddb0) to head (8fbaa2e).

❗ Current head 8fbaa2e differs from pull request most recent head 673731b. Consider uploading reports for the commit 673731b to get more accurate results

Files	Patch %	Lines
preliz/distributions/negativebinomial.py	96.55%	3 Missing ⚠️
preliz/internal/special.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #351      +/-   ##
==========================================
+ Coverage   83.06%   83.14%   +0.07%     
==========================================
  Files          48       49       +1     
  Lines        4890     4929      +39     
==========================================
+ Hits         4062     4098      +36     
- Misses        828      831       +3     

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