Cleanup OOBE M4 logic
Cleanup OOBE M4 logic

* Call coral::micro::led for LED::kUser
* Make g_person_detected volatile
* Make m4_timer recurring
* Replace loop() with vTaskDelay when OOBE_DEMO is defined
* Use single call to turn on/off the LED
* Use unnamed namespace instead of static

Change-Id: If1f50a0c5e9c4898fd345852aeb95c5de4d8bdce
GitOrigin-RevId: 4c7f9c4c2d5bb73387276ca3e045ec5a2ba86421

google-coral/coralmicro,google-coral/coralmicro,google-coral/coralmicro,google-coral/coralmicro,google-coral/coralmicro