FEAT: Adding __iter__ and .next functionality for cursor (#162)

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[AB#34896](https://sqlclientdrivers.visualstudio.com/c6d89619-62de-46a0-8b46-70b92a84d85e/_workitems/edit/34896)
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[AB#34895](https://sqlclientdrivers.visualstudio.com/c6d89619-62de-46a0-8b46-70b92a84d85e/_workitems/edit/34895)

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### Summary   
This pull request enhances the `Cursor` class in `mssql_python` to
support Python's iterator protocol, adds a `next()` method for
compatibility, and introduces comprehensive test cases to validate these
features. The changes improve usability by enabling direct iteration
over query results and ensure backward compatibility with existing code.

### Enhancements to `Cursor` functionality:
* Added `__iter__` and `__next__` methods to the `Cursor` class,
allowing it to be used as an iterator in for-loops and with the `next()`
function. The `next()` method is also included as an alias for
`__next__` to maintain compatibility with older code.
(`mssql_python/cursor.py`,
[[1]](diffhunk://#diff-deceea46ae01082ce8400e14fa02f4b7585afb7b5ed9885338b66494f5f38280R44)
[[2]](diffhunk://#diff-deceea46ae01082ce8400e14fa02f4b7585afb7b5ed9885338b66494f5f38280R540-R581)

### New test cases for iteration and `next()` functionality:
* Introduced `test_chaining_with_iteration` to validate iteration over
query results using for-loops. (`tests/test_004_cursor.py`,
[tests/test_004_cursor.pyR1529-R1774](diffhunk://#diff-82594712308ff34afa8b067af67db231e9a1372ef474da3db121e14e4d418f69R1529-R1774))
* Added `test_cursor_next_functionality` to confirm correct behavior of
the `next()` method, including handling of empty result sets and
single-row queries. (`tests/test_004_cursor.py`,
[tests/test_004_cursor.pyR1529-R1774](diffhunk://#diff-82594712308ff34afa8b067af67db231e9a1372ef474da3db121e14e4d418f69R1529-R1774))
* Created `test_cursor_next_with_different_data_types` to ensure
`next()` handles various data types correctly.
(`tests/test_004_cursor.py`,
[tests/test_004_cursor.pyR1529-R1774](diffhunk://#diff-82594712308ff34afa8b067af67db231e9a1372ef474da3db121e14e4d418f69R1529-R1774))
* Added `test_cursor_next_error_conditions` to test edge cases, such as
calling `next()` on a closed cursor or before executing a query.
(`tests/test_004_cursor.py`,
[tests/test_004_cursor.pyR1529-R1774](diffhunk://#diff-82594712308ff34afa8b067af67db231e9a1372ef474da3db121e14e4d418f69R1529-R1774))
* Developed `test_future_iterator_protocol_compatibility` to demonstrate
future compatibility with Python's iterator protocol.
(`tests/test_004_cursor.py`,
[tests/test_004_cursor.pyR1529-R1774](diffhunk://#diff-82594712308ff34afa8b067af67db231e9a1372ef474da3db121e14e4d418f69R1529-R1774))

### Real-world usage examples:
* Added `test_execute_chaining_compatibility_examples` to showcase
practical use cases of iteration and chaining, such as fetching rows,
updating, and deleting records. (`tests/test_004_cursor.py`,
[tests/test_004_cursor.pyR1826-R1885](diffhunk://#diff-82594712308ff34afa8b067af67db231e9a1372ef474da3db121e14e4d418f69R1826-R1885))

---------

Co-authored-by: Jahnvi Thakkar <jathakkar@microsoft.com>

Author: jahnvi480

mssql_python/constants.py

@@ -97,7 +97,6 @@ class ConstantsDDBC(Enum):
     SQL_ATTR_ROW_ARRAY_SIZE = 27
     SQL_ATTR_ROWS_FETCHED_PTR = 26
     SQL_ATTR_ROW_STATUS_PTR = 25
-    SQL_FETCH_NEXT = 1
     SQL_ROW_SUCCESS = 0
     SQL_ROW_SUCCESS_WITH_INFO = 1
     SQL_ROW_NOROW = 100
@@ -117,6 +116,14 @@ class ConstantsDDBC(Enum):
     SQL_NULLABLE = 1
     SQL_MAX_NUMERIC_LEN = 16
 
+    SQL_FETCH_NEXT = 1
+    SQL_FETCH_FIRST = 2
+    SQL_FETCH_LAST = 3
+    SQL_FETCH_PRIOR = 4
+    SQL_FETCH_ABSOLUTE = 5
+    SQL_FETCH_RELATIVE = 6
+    SQL_FETCH_BOOKMARK = 8
+
 class AuthType(Enum):
     """Constants for authentication types"""
     INTERACTIVE = "activedirectoryinteractive"