PX4 Autopilot through 1.17.0 Use-After-Free in load_mon

PX4 Autopilot through 1.17.0 contains a use-after-free vulnerability in the load_mon module's stop path where exit_and_cleanup() deletes the LoadMon object and frees the performance counter before perf_end() attempts to access it. Attackers can trigger this vulnerability by issuing the load_mon stop command from any PXH or MAVLink shell, causing reads and writes through freed memory that corrupt heap objects and destabilize the flight stack.