fix: prevent duplicate item state from React 18 double render

[YooZiiX]

Summary

This pull request addresses a React 18-related issue where moving an item between Columns and Rows in the PivotTableUI causes duplicated state due to React 18's double rendering behavior in Strict Mode.

Changes

• Introduced a handleDuplicates() utility to filter out duplicate items from state arrays.
• Integrated handleDuplicates() into the propUpdater() method for rows and cols keys.
• Added unit tests to verify that duplicate entries are not introduced during re-renders.