Refactor test runner to use static list of resource paths

Previously everything lived in an inner class method of
SettingsRobolectricTestRunner. That method has now been turned into
a static method so that it can be called by other runners.

Bug: 62460102
Test: robotests
Change-Id: I6612b1f26404587301c534c8ba60e39d59d6c840

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

@@ -31,6 +31,8 @@ import org.robolectric.annotation.Config;
 import static junit.framework.Assert.assertEquals;
 import static junit.framework.Assert.assertTrue;
 
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+
 @RunWith(SettingsRobolectricTestRunner.class)
 @Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
 public class SummaryPreferenceTest {