CAN communication should be separated from AS_STATE logic

[daniel-bara]

Our 'ros-car connector' node, ackermann_can.cpp has too many responsibilities. It currently

1. Handles the VCU's AS_STATE modes
2. Sends messages on CAN bus, publishes /vcu2ai messages on ROS.
3. Handles VCU handshakes

This means it will be difficult to test the logic performed by this node on a small scale car that is not fitted with can bus.

My suggestion is to decouple the CAN bus communication from the AS_STATE logic, so that we can easily switch to a scale car that does not have CAN bus. In the new setup, we would have

• a new node (possibly python) handling the AS_STATEs (1.), and publishing ROS /ai2vcu messages
• a 'ros-car connector' node translating from ROS (/ai2vcu, /vcu2ai) to CAN bus (2.).

This way, we could easily switch out the 'ros-car connector' for whatever communication protocol we want to use on the small scale car and test the rest of the logic.

(3. vcu handshakes - could go to either of them depending on whether we want handshakes on the small scale car or not)