Update customize button title when state changed

- This CL update customize button title when
  onCustomizedButtonStateChanged() is called.
- Add test case

Bug: 152002708
Test: make -j42 RunSettingsRoboTests
Change-Id: I85c9cf90305757e279c058db2875e303b4add437

src/com/android/settings/panel/PanelContent.java

@@ -86,9 +86,9 @@ public interface PanelContent extends Instrumentable {
     }
 
     /**
-     * @return a string for the title of the custom button.
+     * @return a string for the title of the customized button.
      */
-    default CharSequence getCustomButtonTitle() {
+    default CharSequence getCustomizedButtonTitle() {
         return null;
     }