Currently, the charge state machine checks the battery temperature in shutdown_on_critical_battery and charger_profile_override but it doesn't keep it as a state or a flag. (Note BATT_FLAG_BAD_TEMPERATURE indicates temperature is higher than the surface of the sun.)

We should add a state indicating a bad temperature, including too low and too high, where charging or discharging are stopped so that LED controller can reflect it on the LED.