FEAT: Adding Columns API in cursor

[jahnvi480]

Work Item / Issue Reference

AB#34927

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Summary

This pull request adds support for retrieving column metadata from SQL tables via a new columns method on the Cursor class, and exposes the underlying ODBC SQLColumns function through the C++ and Python bindings. The main changes introduce the necessary function pointer, wrapper, and Python binding, as well as the implementation of the new method in Python.

Python API enhancements:

• Added a columns method to the Cursor class in cursor.py that retrieves column information for specified tables using the ODBC SQLColumns function. This method includes documentation, argument handling, and returns a list of Row objects with detailed column metadata.

C++ bindings and driver integration:

• Defined a new function pointer type SQLColumnsFunc, its global variable, and ensured it is loaded from the driver in ddbc_bindings.h and ddbc_bindings.cpp.
• Implemented the SQLColumns_wrap function to call the ODBC SQLColumns API, handling platform differences between Unix and Windows.
• Exposed the new DDBCSQLColumns function to Python via pybind11 in the module definition.