Task redesign v2 pybind apis and fix task testcases

[youliangtan]

This PR is to add support for the new task apis for rmf_fleet_adapter_python, and to fix existing test cases for loop and delivery task requests.

• Depends on: pybind11_json_vendor https://github.com/open-rmf/pybind11_json_vendor for json type conversion is used here.

1. Expand rmf_fleet_adapter_python Bindings

   • added Confirmation and consider_..._requests, api
   • fleet_state_update_period and fleet_state_topic_publish_period
   • Modification of ConsiderRequest function
     • as pass by ref as arg is not supported modification is made in the python api to

     using ModifiedConsiderRequest = std::function<Confirmation(const nlohmann::json &description)>;
     
     ##  typing in python:
     #  consider: Callable[[json], rmf_fleet_adapter::agv::FleetUpdateHandle::Confirmation]

2. Fix Test cases for loop and delivery

• rmf_fleet_adapter_python:

  ros2 run rmf_fleet_adapter_python test_delivery.py
  ros2 run rmf_fleet_adapter_python test_loop.py

• rmf_fleet_adapter

  ./build/rmf_fleet_adapter/test_rmf_fleet_adapter "Scenario: Test Delivery"
  ./build/rmf_fleet_adapter/test_rmf_fleet_adapter "Scenario: Test loop requests"

Additionally, a utility script is created to echo the rmf websocket msgs. Example:

ros2 run rmf_fleet_adapter_python rmf_msg_observer.py --task_state

[mxgrey]

Thanks for taking care of the bindings, and also for working on the tests 🙇

[mxgrey]

Not important enough to change right now, but just a thought: Since we require exactly one of these to be selected, it would probably be more idiomatic to have them as a single positional argument instead of optional flags.