Migrate to Behaviortree.CPP 4

[luca-della-vedova]

Apart from being the latest and greatest it would allow simplifying the implementation of looping introduced in #42.
Specifically, there is a builtin node for going through a std::deque and popping one item at a time so we would be able to fully remove the custom rmf_request.LoopDestination behavior tree node. The custom node was designed to have the same inputs and outputs as the BTCPP4 builtin node so it should be a dropin replacement.

I prototyped with this during the Jazzy migration and found out that it's actually a fairly straightforward change but didn't bundle it in the Jazzy PR to avoid blowing up the complexity.