Move GrootLocomotionController and HolosomaLocomotionController into a new
controllers/ subpackage and add the SONIC whole-body controller
(sonic_pipeline.py, sonic_whole_body.py) plus the examples/unitree_g1/sonic.py
standalone script. UnitreeG1 now honors a controller's kp/kd, calls
controller.shutdown() on disconnect, and skips arm publishing for full_body
controllers.