Added arrayPRAUC function to calculate AUC for Precision Recall curve

Why it matters

The arrayPRAUC function solves the problem of evaluating model performance by providing a method to compute the AUC of Precision-Recall curves directly in ClickHouse. This helps users assess classification models, especially with imbalanced datasets, improving model evaluation capabilities within the database.

How to use it

Use the arrayPRAUC function by passing arrays of precision and recall values to it in your SQL queries. For example:

SELECT arrayPRAUC(precision_array, recall_array) FROM your_table;