* Some components have initialization dependencies. To account for
them, simple numeric priority values are introduced.
* esp_system_init_fn_array moved into Flash from DRAM
* System init functions defined using ESP_SYSTEM_INIT_FN now return
an error code. This enables simpler and more consistent error
handling in the init functions. Returning an error from an init
function is now a valid approach — the startup code will print
an error and abort.
- Introduce system time function and concept of system time provider.
esp_timer is system time provider when present.
- Set the reference point for system time, g_startup_time.
- Use the system time functions in newlib instead of calling esp_timer
functions directly
