Makes it possible to robo-test Settings app fragments.

This adds bunch of shadow/placeholder classes and logic to handle
references to Android internal resources or newly added classes/methods
that Robolectric hasn't yet picked up.

Developers can follow ManageApplicationsTest example to use the shadow
classes and the utility method to start ther fragment in their
robolectric tests.

Bug: 33431346
Test: This is a test improvement CL. RunSettingsRoboTests still passes.
Change-Id: I943ab871631cb8c368d9f9db481c00558c5c4d1f

tests/robotests/src/android/print/PrintServicesLoader.java

@@ -0,0 +1,19 @@
+package android.print;
+
+import android.annotation.NonNull;
+import android.content.Context;
+import android.content.Loader;
+import android.printservice.PrintServiceInfo;
+import com.android.internal.util.Preconditions;
+
+import java.util.List;
+
+/**
+ * A placeholder class to prevent ClassNotFound exceptions caused by lack of visibility.
+ */
+public class PrintServicesLoader extends Loader<List<PrintServiceInfo>> {
+    public PrintServicesLoader(@NonNull PrintManager printManager, @NonNull Context context,
+            int selectionFlags) {
+        super(Preconditions.checkNotNull(context));
+    }
+}