[Provider Model] Add progress bar to internet panel

- Show progress bar when Wi-Fi scanning

- Show "Searching for networks..." sub-title when Wi-Fi scanning

- Remove "Wi-Fi" from searching networks string

Bug: 178774497
Test: manual test
atest -c InternetConnectivityPanelTest
make RunSettingsRoboTests ROBOTEST_FILTER=PanelFragmentTest

Change-Id: Ic05b939bef3b106845fe90db41eb09f0e15756f4

tests/robotests/src/com/android/settings/panel/FakePanelContent.java

@@ -48,6 +48,7 @@ public class FakePanelContent implements PanelContent {
     private int mViewType;
     private boolean mIsCustomizedButtonUsed = false;
     private CharSequence mCustomizedButtonTitle;
+    private boolean mIsProgressBarVisible;
 
     @Override
     public IconCompat getIcon() {
@@ -117,4 +118,13 @@ public class FakePanelContent implements PanelContent {
     public void setCustomizedButtonTitle(CharSequence title) {
         mCustomizedButtonTitle = title;
     }
+
+    @Override
+    public boolean isProgressBarVisible() {
+        return mIsProgressBarVisible;
+    }
+
+    public void setIsProgressBarVisible(boolean isProgressBarVisible) {
+        mIsProgressBarVisible = isProgressBarVisible;
+    }
 }