Logging in series of examples has misuse of "%d" instead of type-appropriate format specifiers.
Fix by changing "%d" to PRIxx macros corresponding to type.
Remove -Wno-format compile flag in those examples that are affected.
This updates the minimal supported version of CMake to 3.16, which in turn enables us to use more CMake features and have a cleaner build system.
This is the version that provides most new features and also the one we use in our latest docker image for CI.
esp_netif_init() returns standard esp_err_t error code (unlike tcpip_adapter init), so shall be checked for the return value
Also to make the initialization code more consistent.
