Migration from Gazebo classis to gazebo harmonic and ROS1 to ROS2 for 3_simulation_gazebo package

[aPR0T0]

[NECESSARY CHANGES]:

• Change URDF to SDF
  • Reference
  • Things to be considered in this migration
    - While converting directly to .sdf make sure of the controllers from ros2_control
    - First try to understand how the controllers are used in this example
    - Clone the above example and try launching rrrobot example and observe the code as it will be helpful for this migration
    - Try using position controllers for the rotational joints
• Rewrite the .launch scripts to .launch.py
  • For this one can refer this repo here
  • NOTE: This repo works for the gazebo classic with position controllers
• Rewrite the inverse kinematics script for rclpy and utilize position controller to control the joints

[OPTIONAL CHANGES]:

• Writing a smoother angle change for inverse kinematics

[FUTURE PROSPECTS]:

• Writing script for inverse velocity kinematics