Add effort command interface to hardware interface (backport #1411)

[mergify]

This is just a proof of concept to make the robot work. This still requires some work.

Requires UniversalRobots/Universal_Robots_ROS2_Description#302 to effectively work.

---

Update

With 9e98ec2 this should be compatible with

• robot software versions not supporting torque control
• descriptions not exposing an effort command interface for the joints

With those, the feature added from this PR will effectively be useless / not available with the correct user feedback where necessary. For example, when trying to activate an effort controller with a robot running 5.22.0:

[ros2_control_node-1] [ERROR 2025-10-08 09:02:09.792] [controller_manager.hardware_component.system.ur5e]: Requested to use effort interface on a robot version that doesn't support it. Torque control is available from robot software 5.23.0 / 10.10.0 on.                                                               
[ros2_control_node-1] [ERROR 2025-10-08 09:02:09.792] [controller_manager]: Component 'ur5e' did not accept command interfaces combination:                                                                                                                                                                                 
[ros2_control_node-1] Start interfaces:                                                                                                                                                                                                                                                                                     
[ros2_control_node-1] [                                                                                                                                                                                                                                                                                                     
[ros2_control_node-1]   shoulder_pan_joint/effort                                                                                                                                                                                                                                                                           
[ros2_control_node-1]   shoulder_lift_joint/effort                                                                                                                                                                                                                                                                          
[ros2_control_node-1]   elbow_joint/effort                                                                                                                                                                                                                                                                                  
[ros2_control_node-1]   wrist_1_joint/effort                                                                                                                                                                                                                                                                                
[ros2_control_node-1]   wrist_2_joint/effort                                                                                                                                                                                                                                                                                
[ros2_control_node-1]   wrist_3_joint/effort                                                                                                                                                                                                                                                                                
[ros2_control_node-1] ]                                                                                                                                                                                                                                                                                                     
[ros2_control_node-1] Stop interfaces:                                                                                                                                                                                                                                                                                      
[ros2_control_node-1] [                                                                                                                                                                                                                                                                                                     
[ros2_control_node-1] ]

ToDo's:

• Implementation
• Test on a real robot
• Test in simulation (torque control doesn't work with URSim)
• Write tests (torque control doesn't work with URSim -- we cannot test much)
• Write documentation

---

This is an automatic backport of pull request #1411 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of c1cb7f2 has failed:

On branch mergify/bp/humble/pr-1411
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit c1cb7f2.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   ur_robot_driver/config/ur_controllers.yaml
	new file:   ur_robot_driver/doc/hardware_interface.rst
	modified:   ur_robot_driver/include/ur_robot_driver/hardware_interface.hpp
	modified:   ur_robot_driver/launch/ur_control.launch.py
	modified:   ur_robot_driver/src/hardware_interface.cpp
	modified:   ur_robot_driver/test/integration_test_controller_switch.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   ur_robot_driver/doc/index.rst

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally