Enhance _set_value_from_template to support Redner integration

- Fix typo in `placeholderRednerField` → `placeholderRenderField`
- Validate `converterField` as string type

Requires a Odoo with [ADD] *: pypdf 3.x compatibility (https://github.com/odoo/odoo/commit/fddf53c9b6bcaea1a9ff7e041c0ccbb65a4647c8)

Reuse odoo guess mimetype code and compatibility code between different versions of python-magic.

Also factorize some code and add comment.

- Introduced a button to dynamically set the expression in the substitution line.
- The feature is available for converters of type "Odoo template", "Odoo template + Evaluation", and "Field".
- Added functionality to visualize how to define each converter, displaying a placeholder (example) for each converter type.
- The code has been designed to ease the integration of additional converters in the future.
- Refactored the code to improve performance and stability.

- Add missing python-magic requirement for package