tests(column): enhance column function code coverage (#68)

* Add test for ascending order with NULLs first.

* feat(tests): add test for ascending order with NULLs first (#17)

    * feat(tests): implement `test_func_asc_nulls_first`
      - Verify sorting functionality for ascending order with NULL values positioned first.

* feat(tests): add test for ascending order with NULLs last (#17)

    * feat(tests): implement `test_func_asc_nulls_last`
      - Verify sorting functionality for ascending order with NULL values positioned last.

* feat(tests): add tests for descending order with NULLs first and last (#49)

    * feat(tests): implement `test_func_desc_nulls_first`
      - Verify sorting functionality for descending order with NULL values positioned first.

    * feat(tests): implement `test_func_desc_nulls_last`
      - Verify sorting functionality for descending order with NULL values positioned last.

    * validate robustness and accuracy of the sorting mechanism

* feat(tests): add tests for descending order with NULLs first and last (#17)

    * feat(tests): implement `test_func_desc_nulls_first`
      - Verify sorting functionality for descending order with NULL values positioned first.

    * feat(tests): implement `test_func_desc_nulls_last`
      - Verify sorting functionality for descending order with NULL values positioned last.

    * validate robustness and accuracy of the sorting mechanism

* feat(tests): add test for LIKE filter functionality (#17)

    * feat(tests): implement `test_func_like`
      - Verify filter functionality using the LIKE operator.
      - Ensure the filter correctly selects the name "Alice".

    * validate robustness and accuracy of the LIKE filter mechanism

* feat(tests): add test for ILIKE filter functionality (#17)

    * feat(tests): implement `test_func_ilike`
      - Verify filter functionality using the ILIKE operator.
      - Ensure the filter correctly selects the name "Alice" using a case-insensitive pattern "%Ice".

    * validate robustness and accuracy of the ILIKE filter mechanism

* feat(tests): add test for RLIKE filter functionality (#17)
   * feat(tests): implement
     - Implemented a test to validate the behavior of the 'rlike' filter on a DataFrame.
     - Ensured that the filter correctly identifies records with names matching the regex pattern ice.
       - Added necessary setup and assertions for expected results.

* feat(tests): add test for RLIKE filter functionality (#17)
   * feat(tests): implement `test_func_rlike`
     - Implemented a test to validate the behavior of the 'rlike' filter on a DataFrame.
     - Ensured that the filter correctly identifies records with names matching the regex pattern ice.
     - Added necessary setup and assertions for expected results.

* feat(tests): add test for EQ filter functionality (#17)
    * feat(tests): implement `test_func_eq`
      - Verify filter functionality using the EQ operator.

* feat(tests): add test for OR filter functionality (#17)
    * feat(tests): implement `test_func_or`
      - Verify filter functionality using the OR operator.
      - Ensure the filter correctly selects the name "Alice" using a case-insensitive pattern "%Ice".

    * validate robustness and accuracy of the ILIKE filter mechanism
 main

* feat(tests): add test for IS_NULL filter functionality (#17)
   * feat(tests): implement `test_func_is_null`
     - Implemented a test to validate the behavior of the 'is_null' filter on a DataFrame.
     - Ensured that the filter correctly identifies records with null values.
     - Added necessary setup and assertions for expected results.

* Exclude additional is_null test.

* feat(tests): add test for IS_NOT_NULL filter functionality (#17)
   * feat(tests): implement `test_func_is_not_null`
     - Implemented a test to validate the behavior of the 'isnotnull' filter on a DataFrame.
     - Ensured that the filter correctly identifies records with non-null values.
     - Added necessary setup and assertions for expected results.
     - Moved `isnotnull` function definition to `
        // functions that require a single col argument
        generate_functions!(
            one_col: isnan,
            isnull,
            isnotnull,
            ...)
     `

* feat(tests): add tests for window functions and IS_NAN filter functionality(#17)

* feat(tests): implement `test_func_over`
  - Implemented a test to validate the behavior of window functions on a DataFrame.
  - Ensured that the window functions (`rank` and `min`) correctly compute values within the specified window.
  - Added necessary setup, sorting, and assertions for expected results.

* feat(tests): implement `test_func_isnan`
  - Implemented a test to validate the behavior of the `isnan` function on a DataFrame.
  - Ensured that the `isnan` function correctly identifies NaN values.
  - Added necessary setup and assertions for expected results.

* feat(tests): add tests for column aliasing, casting, and substring functions (#17)

- feat(tests): implement `test_func_cast`
  - Added a test to validate the behavior of casting an integer column to a string.
  - Ensured that the cast operation correctly transforms the data type and assigns the alias.

- feat(tests): implement `test_func_alias`
  - Added a test to verify column aliasing functionality.
  - Confirmed that the DataFrame correctly applies aliases to columns.

- feat(tests): implement `test_func_substr`
  - Added a test to validate the substring function on a string column.
  - Ensured that the substring operation works as expected and assigns the alias.

* feat(fix): Fixed typo on test name - test_func_substract to test_func_subtract.