Use gpiod in OLED script

OLED script cannot register GPIO to monitor power outage on a Raspberry Pi 5 since it uses RPi.GPIO. 

```
Traceback (most recent call last):
  File "/home/rak/workspace/rakpios/stage2-rak/03-utils/files/oled", line 345, in <module>
    GPIO.setup(16, GPIO.IN, pull_up_down=GPIO.PUD_UP)
RuntimeError: Cannot determine SOC peripheral base address
```

Update code to use gpiod instead.
