Updates for ros2 template

[chenjunnn]

• Use ament_cmake_auto to simplify CmakeLists
• Format cpp files using ament_uncrusify
• Use rclcpp components to build nodes
• Update ROS2 launch file using Python (.launch.py)
• changed files name to under_scored style according to cpp code style guide 4.3 in ROS Wiki

I only tested my code on ROS2 Galactic.