Add logging for SettingsPanels

The 3 main categories are:
- Panel Opened
- Panel Closed
- Panel Slice interaction

There are 3 close events:
- See more button
- Done button
- Clicking outside the panel

Slice interactions will log the Uri of the Slice and the ActionType,
such as Toggle, Slider, Content (intent).

Change-Id: Iecad948f39f50dd12ae1bcb23a5d523e0df8bb98
Fixes: 117804231
Test: robotests

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

@@ -50,4 +50,9 @@ public class NfcPanel implements PanelContent {
         intent.setClassName(mContext.getPackageName(), SubSettings.class.getName());
         return intent;
     }
+
+    @Override
+    public int getMetricsCategory() {
+        return SettingsEnums.PANEL_NFC;
+    }
 }