Handle additional robot types

[irisxu02]

Add handling of different robot types which may have different configurations of launch arguments (package dependencies, file paths, args used in xacro, etc.).
The user should only be required to modify the arms.json file to specify arm type to create a new robot of that type.

Ideally the user can add a new robot type by including:

• the robot description
  • SDF or URDF or XACRO (XACRO renders to URDF and Gazebo sim automatically converts URDF to SDF)
  • if using XACRO, any arguments that need to be passed to it,
• an RVIZ file (could be optional? unless path planning requires it TBD)

[irisxu02]

Launching a single viperx 300s in gazebo sim 07400f7
Will need to include the modified files of the interbotix_xsarm_descriptions package, since original only supports Gazebo classic.

[irisxu02]

TODOs:

• clean install interbotix_ros_manipulators - fix RVIZ not loading issue and tools not being built.
  • needed to also launch joint_state_publisher or joint_state_publisher_gui

[irisxu02]

To run the example ros2 launch interbotix_xsarm_sim xsarm_gz_classic.launch.py robot_model:=vx300s, which uses gazebo classic, we need to source Gazebo setup first . /usr/share/gazebo/setup.sh.
Interbotix/interbotix_ros_manipulators#182 (comment)

[irisxu02]

Ensure that the function DeclareInterbotixXSArmRobotDescriptionLaunchArgument uses custom xsarm_descriptions package to generate the robot description (in the file: interbotix_xs_modules/xs_launch/xs_launch.py).

• include any modified interbotix packages as submodules? Maybe from a fork