Add source code for functions touching the struct netif to better support lwip development: sdk_wifi_get_ip_info, sdk_wifi_set_ip_info, sdk_wifi_get_macaddr, sdk_wifi_set_macaddr.
Also code for sdk_wifi_station_get_connect_status.
Also code for wifi_get_sleep_type and set_sleep_type, noting wifi_set_sleep_type returns a bool success flag, and implement wifi_get_sleep_type using sdk_pm_get_sleep_type.
Also comment the point at which the bus clock that drives the uart changes on startup and comment out the change in the uart divisor. This at least allows a consistent uart baud rate during a restart if using the rate 115200.
* wifi_set_sleep_type returns a bool success flag.
* wifi_get_sleep_type seemed useless, just returning an argument. Added an implementation using sdk_pm_get_sleep_type.
