Make prediction column optional for performance estimation / calculation.

[nnansters]

This PR makes the y_pred column name optional for realised and estimated performance calculators in binary classification problem types.

When no y_pred column is given, only AUROC and average precision are allowed as metric values.

[codecov]

Codecov Report

Attention: Patch coverage is 95.83333% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 78.58%. Comparing base (e98cab9) to head (b6d8bdf).

Files	Patch %	Lines
nannyml/performance_calculation/calculator.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #380      +/-   ##
==========================================
+ Coverage   78.41%   78.58%   +0.16%     
==========================================
  Files         110      110              
  Lines        8520     8540      +20     
  Branches     1514     1522       +8     
==========================================
+ Hits         6681     6711      +30     
+ Misses       1476     1465      -11     
- Partials      363      364       +1     

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