esp8266: Use extmod/modnetwork.c instead of port-specific version.

Rather than duplicating the implementation of `network`, this allows
ESP8266 to use the shared one in extmod.  In particular this gains access
to network.hostname and network.country.

Other than adding these two methods, there is no other user-visible change.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

ports/esp8266/boards/esp8266_common.ld

@@ -163,12 +163,12 @@ SECTIONS
         *machine_hspi.o(.literal*, .text*)
         *hspi.o(.literal*, .text*)
         *modesp.o(.literal* .text*)
-        *modnetwork.o(.literal* .text*)
         *moduos.o(.literal* .text*)
         *modutime.o(.literal* .text*)
         *modlwip.o(.literal* .text*)
         *modsocket.o(.literal* .text*)
         *modonewire.o(.literal* .text*)
+        *network_wlan.o(.literal* .text*)
         *esp_mphal.o(.literal* .text*)
 
         /* we put as much rodata as possible in this section */