esp_timer_get_time returns monotonic time in microseconds, as a 64-bit
number. It can be called from tasks and interrupts, does not use any
critical sections/mutexes, and is thread safe.
currently ```esp_wifi_init``` have to be called in ```app_main``` or
WiFi will fail to boot. When possible to boot later, code will be moved
into ```_esp_wifi_start``` to be executed when necessary
IDF Options:
- Autostart Arduino (implements app_main)
- Disable HAL locks
- Set HAL debug level
- Auto-connect STA if configured (else will connect after WiFi.begin())
