Refer to the last Hotspot password when generating the password

- Query the last Hotspot password when security type is SECURITY_TYPE_OPEN and it will be used when the user changes to another security type

- If the last hotspot password is an empty string, then generate random password

Bug: 201789473
Test: manual test
atest -c WifiHotspotRepositoryTest
make RunSettingsRoboTests ROBOTEST_FILTER=WifiTetherPasswordPreferenceControllerTest

Change-Id: Id3a846099238433e7b6c8b934fa26a74df0dcb61

src/com/android/settings/overlay/FeatureFactory.java

@@ -48,6 +48,7 @@ import com.android.settings.slices.SlicesFeatureProvider;
 import com.android.settings.users.UserFeatureProvider;
 import com.android.settings.vpn2.AdvancedVpnFeatureProvider;
 import com.android.settings.wifi.WifiTrackerLibProvider;
+import com.android.settings.wifi.factory.WifiFeatureProvider;
 import com.android.settingslib.core.instrumentation.MetricsFeatureProvider;
 
 /**
@@ -192,6 +193,11 @@ public abstract class FeatureFactory {
      */
     public abstract AdvancedVpnFeatureProvider getAdvancedVpnFeatureProvider();
 
+    /**
+     * Retrieves implementation for Wi-Fi feature.
+     */
+    public abstract WifiFeatureProvider getWifiFeatureProvider();
+
     public static final class FactoryNotFoundException extends RuntimeException {
         public FactoryNotFoundException(Throwable throwable) {
             super("Unable to create factory. Did you misconfigure Proguard?", throwable);