cpu_logger.py: add CPU temp and speed logging

[ElectricRCAircraftGuy]

Begin logging CPU temp and CPU clock speed (since it's variable) each log iteration too, to try to identify if the heat sink is bad and/or the heat sink thermal paste. It's possible the thermal paste is dried up or the heat sink loose, which could make the CPU get hot, then because it's hot, the CPUs get throttled to a lower speed, then because they are throttled, the % CPU usage goes up!--not because the workload increased, but because the ability to perform the work decreased.