Add device name to About Phone page.

The device name is reflected in three places: A Settings.Global flag
which can be read by third party apps, the Bluetooth device name, and
the Wi-Fi tethering hotspot name.

The Bluetooth and Wi-Fi names can be changed independently of the device
name, but if the user sets the device name, they are all changed in
parallel.

Due to the naming restrictions of Bluetooth devices and SSIDs, the SSID
naming restrictions apply to the device name.

Bug: 63819909
Test: Robotest
Change-Id: I3a81535fc07d183557a6fa5d54baef3c7868499c

src/com/android/settings/wifi/tether/WifiTetherSSIDPreferenceController.java

@@ -35,10 +35,12 @@ public class WifiTetherSSIDPreferenceController extends WifiTetherBasePreference
     static final String DEFAULT_SSID = "AndroidAP";
 
     private String mSSID;
+    private WifiDeviceNameTextValidator mWifiDeviceNameTextValidator;
 
     public WifiTetherSSIDPreferenceController(Context context,
             OnTetherConfigUpdateListener listener) {
         super(context, listener);
+        mWifiDeviceNameTextValidator = new WifiDeviceNameTextValidator();
     }
 
     @Override
@@ -70,7 +72,7 @@ public class WifiTetherSSIDPreferenceController extends WifiTetherBasePreference
 
     @Override
     public boolean isTextValid(String value) {
-        return !WifiUtils.isSSIDTooLong(value) && !WifiUtils.isSSIDTooShort(value);
+        return mWifiDeviceNameTextValidator.isTextValid(value);
     }
 
     public String getSSID() {