Close panel when media stop

-Add forceClose callback to finish panel
-Add test cases

Bug: 151396986
Test: make -j50 RunSettingsRoboTests
Change-Id: Ic0ac2880a4ff412382816ccb41b4fbb60dbdf519

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

@@ -32,4 +32,9 @@ public interface PanelContentCallback {
      * a group
      */
     void onHeaderChanged();
+
+    /**
+     * It will be called when panel requests to close itself.
+     */
+    void forceClose();
 }