Work order ID and task ID

[aaronchongth]

Addresses #63 (comment)

This will help with creating unique workcell task IDs, to be used for signals in parallel work orders, #63

• Added work order ID, renamed ID to task ID where applicable, migrate changes and populate fields
• removed step ID per discussion, update tests
• removed number from work orders as well
• generate task ID as {work_order_id}/{process_id}/{step_index}, where step_index is the index of this step in the whole list, starting from 0
• added test for parallel duplicated orders just with different work order IDs

Verify

# Run demo
ros2 launch nexus_demos launch.py headless:=0

# Run work order
cd ~/ws_nexus/src/nexus/nexus_demos/
ros2 action send_goal /system_orchestrator/execute_order nexus_orchestrator_msgs/action/ExecuteWorkOrder "{order: {id: '1', work_order: '$(cat config/pick_and_place.json)'}}"

# Check topics, verify that work order ID is populated by the goal action ID , task ID is populated with {work_order_id}/{process_id}/{step_index}
ros2 topic echo /workcell_1/workcell_state
ros2 topic echo /workcell_2/workcell_state