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[AB#34927](https://sqlclientdrivers.visualstudio.com/c6d89619-62de-46a0-8b46-70b92a84d85e/_workitems/edit/34927)

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### Summary   
This pull request adds support for retrieving column metadata from SQL
Server using the ODBC `SQLColumns` API, and exposes this functionality
to Python through the `columns()` method on the `cursor` class. The
implementation includes both backend C++ bindings and a high-level
Python interface, as well as careful handling of cursor state and result
set mapping.

The most important changes are:

**Python interface:**

* Added a new `columns()` method to the `cursor` class in
`mssql_python/cursor.py` to retrieve detailed column metadata for tables
using the ODBC `SQLColumns` function. This method includes extensive
documentation, result mapping, and warnings about potentially expensive
queries. It also wraps and overrides the fetch methods to provide
specialized column mappings for the result set.

* Updated the `execute()` method in `cursor.py` to restore the original
fetch methods if they were previously overridden, ensuring correct
behavior after using `columns()`.

**C++ bindings and backend:**

* Added the `SQLColumnsFunc` typedef, function pointer, and symbol
loading for the `SQLColumnsW` ODBC API in `ddbc_bindings.h` and
`ddbc_bindings.cpp`. This ensures the backend can call the ODBC function
for column metadata.

* Implemented the `SQLColumns_wrap` C++ function in `ddbc_bindings.cpp`
to call the ODBC `SQLColumns` API, handling both Windows and Unix
platforms, and converting Python objects to wide strings as needed.

* Exposed a new `DDBCSQLColumns` method in the Python extension module,
allowing Python code to call the new backend functionality.

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Co-authored-by: Jahnvi Thakkar <[email protected]>