Add laser, killswitch, and LED hardware interfaces

[dwarakeshbaraneetharan]

 - Added laser_ros2_control for spectrometry laser GPIO control
 - Added killswitch_ros2_control for drive killswitch system
 - Added led_ros2_control for status LED control
 - Integrated new HWIs into athena_science.urdf.xacro
 - Added controller configurations in athena_science_controllers.yaml

[IshanDutta11]

Address some of the minor issues I have. Again, I don't expect this to be in a functioning state yet, I just want them to exist and be testable without failing instantly at a software level.

One other issue is that there are no spawners for the gpio controllers in your launch files. This means that although the hardware interfaces are loaded, the command interfaces remain unclaimed. You cannot test them in this state (I tried candump for example and nothing for your new hwis appeared).

For the laser, you can keep the GPIO controller and we can test with that, but another thing we will need for competition is a service to be exposed allowing us to turn it on and off in Henry's manual controller. I am unsure if he has made anything for the laser, so cooperate with him on this.

Keep in mind, for competition, I would prefer to make our own controller which has services for the gpio functionality instead of publishers. I think this will be a lot easier honestly. I think the only case where I don't really like that is if we want continuous color control for the LEDs and maybe even the Laser. Don't worry about that for now, we will address it in the next pull request, I would just like to hear your thoughts.

Overall, this is probably the most impressive thing I have seen on integration thus far. Very well done, some of the things I expected you to forget like one-and-done sending you got. Fix these small issues, try them on the rover, and I will approve the request.