Backport: Fix NON_UNIQUE value inconsistency in DatabaseMetaData.getIndexInfo()

[Ananya2]

Overview
This PR backports the fix from #2773 into the release/13.2 branch.

Problem

DatabaseMetaData.getIndexInfo() was returning incorrect NON_UNIQUE values due to inconsistent handling between sp_statistics and sys.indexes result sets.

• sp_statistics: NON_UNIQUE with 1 = not unique, 0 = unique
• sys.indexes: is_unique with 1 = unique, 0 = not unique

The method was merging results from both sources without properly converting the sys.indexes.is_unique values to the expected JDBC NON_UNIQUE format, causing the same index to appear as both unique and non-unique.

Solution

• Added proper conversion logic: CASE WHEN i.is_unique = 1 THEN 0 ELSE 1 END AS NON_UNIQUE
• Applied consistent NON_UNIQUE value mapping across all index queries
• Ensured compatibility with both regular SQL Server and Azure Synapse Analytics

Testing

• Verified correct NON_UNIQUE values for unique and non-unique indexes

Closes #2771