Bump minimum Python version

Current minimal python version is 3.7, principally due to PyBind dependencies.

However, a lot of functionalities have appeared since then.

• Introduction of built-in typehint for list, dict (3.9)
• Better error message (3.10)
• Union typehint is now built-in (3.10)
• Self typehint is now built-in (3.11)
• Support of TypeVar, allow to define new type (3.11)
• Performance imporvement (specially regarding C API calls (3.11)
• C BufferProtocol now expose to Python side (3.12)
• Better kwargs typing (3.12)

The discussion I want to open with this issue is do you think we should upgrade Python and to which version ?