Add test to ensure all future fragments implements logging.

The idea is: if a class is Fragment, it must also implements
Instrumentable.

To make the test possible, I added a structure to load all classes in
current classloader, and filter to only the ones we care about. Then
insepct each class definition using reflection.

Bug: 32952614
Test: make RunSettingsRoboTests
Change-Id: Ifa5e27c41d5ad0e84b6e9e9df81c96e8be2878c5

tests/robotests/src/com/android/settings/SettingsDialogFragmentTest.java

@@ -17,6 +17,7 @@ package com.android.settings;
 
 import android.app.Dialog;
 import android.app.Fragment;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;