Add message for y interface of Binomial Polya

[ismailsenoz]

Add predictive distribution for BinomialPolya node

This PR implements the predictive distribution for the BinomialPolya node using Pólya-Gamma augmentation. The implementation includes:

• Message passing rule for predictive distribution
• Support for both analytical and Monte Carlo approximations

Key features:

• Analytical approximation using mean of β when meta is nothing
• Monte Carlo sampling with configurable number of samples when meta is provided
• Returns Binomial distribution with averaged success probability

Files changed:

• src/rules/binomial_polya/y.jl: Added predictive distribution rule
• test/rules/binomial_polya/y_tests.jl: Tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.59%. Comparing base (edaa93c) to head (1632b8d).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #443      +/-   ##
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+ Coverage   73.53%   73.59%   +0.05%     
==========================================
  Files         194      195       +1     
  Lines        5582     5593      +11     
==========================================
+ Hits         4105     4116      +11     
  Misses       1477     1477              

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