Add test coverage for initcap function in hive catalog namespace

[Copilot]

The initcap function was already implemented and registered in the hive function namespace but lacked proper test coverage. This PR adds comprehensive test cases to ensure the function works correctly.

Changes Made

1. Added test cases in TestHiveScalarFunctions.java to verify initcap function behavior:

   • Converts lowercase strings: initcap('hello world') → 'Hello World'
   • Converts uppercase strings: initcap('HELLO WORLD') → 'Hello World'
   • Handles mixed case strings: initcap('hELLo WoRLd') → 'Hello World'

2. Created TestInitCapFunction.java with a unit test to verify the function is properly registered in the hive function registry.

Background

The initcap function was already fully implemented:

• Registered in FunctionRegistry.java at line 219: system.registerGenericUDF("initcap", GenericUDFInitCap.class)
• Uses Hive's GenericUDFInitCap class for the actual implementation
• Available under the hive.default. namespace

This PR ensures the function has proper test coverage and verification, completing the requirement to have the initcap function available and tested under the hive catalog namespace.

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