Migrate to later python-can (>=4)

A lot of distributions are shipping python-can>=4. We are limiting it to python-can>=3.3.3,<4.

Unfortunately support for later python-can requires a refactoring of the code.

Traceback with python-can-4.3.1":

[...]
  File "/home/fab/expliot/expliot/plugins/can/canfuzz.py", line 6, in <module>
    from expliot.core.protocols.hardware.can import CanBus, CanMessage
  File "/home/fab/expliot/expliot/core/protocols/hardware/can/__init__.py", line 7, in <module>
    class CanBus(Bus):
TypeError: function() argument 'code' must be code, not str