Protocol: Separate ContextHandler instances for running on robot and definition #28
Description
Otherwise if we were to run a Protocol and then keep defining things, the Context would be messed up from the Protocol run.
Not an issue when we replay the entire Protocol definition, but it does become an issue when we're using next to run one step at a time, for example in tests.
Plus the MotorControlHandler can pollute the ContextHandler with things that would put it in a different state than during the definition phase alone.