Renamed `find_field_with_sort_order` to `parse_sorted_field`.

- Updated the `find_field_with_sort_order` function to return
`(expression, None)` when the regex doesn't match.
- This provides clearer feedback by preserving the original expression.

Note that we implemented sorting functionality and added unit tests.

The changes include:

- Creation of a new utility file `utils/sorting.py` implementing sorting
functionalities such as :
`find_field_with_sort_order`,
`parse_fields_with_sort_directions`, and `sortkey`.
- Addition of a new file `tests/test_sorting.py` containing unit tests for
sorting logic.

& latest xcg/templates/odoo_module.