esp_event_loop.h and esp_event_loop_init() are depreciated in ESP-IDF v4.x

[UncleGrumpy]

The esp_event_loop has been depreciated in version 4 of the ESP-IDF and has been replaced by the updated esp_event component. The code that is most affected by this change is network_driver.c, but several other sources include esp_event_loop.h and will need to be updated as well.